diff --git a/lib/build.gradle.kts b/lib/build.gradle.kts
index e04c5562..80c18b31 100644
--- a/lib/build.gradle.kts
+++ b/lib/build.gradle.kts
@@ -1,3 +1,9 @@
+/*
+ * This file is part of bitfireAT/synctools which is released under GPLv3.
+ * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
 plugins {
     alias(libs.plugins.android.library)
     alias(libs.plugins.kotlin.android)
@@ -117,6 +123,9 @@ dependencies {
         exclude(group = "org.freemarker")
     }
 
+    // synctools.test package also provide test rules
+    implementation(libs.androidx.test.rules)
+
     // instrumented tests
     androidTestImplementation(libs.androidx.test.rules)
     androidTestImplementation(libs.androidx.test.runner)
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidCalendarTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidCalendarTest.kt
index 3e0ebbb4..e3180c01 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidCalendarTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidCalendarTest.kt
@@ -17,7 +17,6 @@ import android.provider.CalendarContract.Colors
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
 import at.bitfire.ical4android.impl.TestCalendar
-import at.bitfire.ical4android.impl.TestEvent
 import at.bitfire.ical4android.util.MiscUtils.asSyncAdapter
 import at.bitfire.ical4android.util.MiscUtils.closeCompat
 import net.fortuna.ical4j.model.property.DtEnd
@@ -109,12 +108,12 @@ class AndroidCalendarTest {
         val cal = TestCalendar.findOrCreate(testAccount, provider)
         try {
             // add event with color
-            TestEvent(cal, Event().apply {
+            AndroidEvent(cal, Event().apply {
                 dtStart = DtStart("20210314T204200Z")
                 dtEnd = DtEnd("20210314T204230Z")
                 color = Css3Color.limegreen
                 summary = "Test event with color"
-            }).add()
+            }, "remove-colors").add()
 
             AndroidCalendar.removeColors(provider, testAccount)
             assertEquals(0, countColors(testAccount))
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidEventTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidEventTest.kt
index c206d8f8..cd393a90 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidEventTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/AndroidEventTest.kt
@@ -5,13 +5,13 @@
  */
 package at.bitfire.ical4android
 
-import android.Manifest
 import android.accounts.Account
 import android.content.ContentProviderClient
 import android.content.ContentUris
 import android.content.ContentValues
 import android.database.DatabaseUtils
 import android.net.Uri
+import android.os.Build
 import android.provider.CalendarContract.ACCOUNT_TYPE_LOCAL
 import android.provider.CalendarContract.AUTHORITY
 import android.provider.CalendarContract.Attendees
@@ -21,13 +21,12 @@ import android.provider.CalendarContract.ExtendedProperties
 import android.provider.CalendarContract.Reminders
 import androidx.core.content.contentValuesOf
 import androidx.test.platform.app.InstrumentationRegistry.getInstrumentation
-import androidx.test.rule.GrantPermissionRule
 import at.bitfire.ical4android.impl.TestCalendar
-import at.bitfire.ical4android.impl.TestEvent
 import at.bitfire.ical4android.util.AndroidTimeUtils
 import at.bitfire.ical4android.util.DateUtils
 import at.bitfire.ical4android.util.MiscUtils.asSyncAdapter
 import at.bitfire.ical4android.util.MiscUtils.closeCompat
+import at.bitfire.synctools.test.InitCalendarProviderRule
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateList
 import net.fortuna.ical4j.model.DateTime
@@ -59,9 +58,11 @@ import org.junit.Before
 import org.junit.BeforeClass
 import org.junit.ClassRule
 import org.junit.Test
+import org.junit.rules.TestRule
 import java.net.URI
 import java.time.Duration
 import java.time.Period
+import java.util.UUID
 import java.util.logging.Logger
 import kotlin.collections.plusAssign
 
@@ -71,10 +72,7 @@ class AndroidEventTest {
 
         @JvmField
         @ClassRule
-        val permissionRule = GrantPermissionRule.grant(
-            Manifest.permission.READ_CALENDAR,
-            Manifest.permission.WRITE_CALENDAR
-        )
+        val initCalendarProviderRule: TestRule = InitCalendarProviderRule.getInstance()
 
         lateinit var provider: ContentProviderClient
 
@@ -171,7 +169,8 @@ class AndroidEventTest {
                 dtStart = DtStart(DateTime())
             eventBuilder()
         }
-        val uri = TestEvent(calendar, event).add()
+        // write event with random file name/sync_id
+        val uri = AndroidEvent(calendar, event, syncId = UUID.randomUUID().toString()).add()
         provider.query(uri, null, null, null, null)!!.use { cursor ->
             cursor.moveToNext()
             val values = ContentValues(cursor.columnCount)
@@ -180,7 +179,7 @@ class AndroidEventTest {
         }
     }
 
-    private fun firstExtendedProperty(values: ContentValues, mimeType: String): String? {
+    private fun firstExtendedProperty(values: ContentValues): String? {
         val id = values.getAsInteger(Events._ID)
         provider.query(ExtendedProperties.CONTENT_URI.asSyncAdapter(testAccount), arrayOf(ExtendedProperties.VALUE),
                 "${ExtendedProperties.EVENT_ID}=?", arrayOf(id.toString()), null)?.use {
@@ -191,7 +190,7 @@ class AndroidEventTest {
     }
 
     private fun firstUnknownProperty(values: ContentValues): Property? {
-        val rawValue = firstExtendedProperty(values, UnknownProperty.CONTENT_ITEM_TYPE)
+        val rawValue = firstExtendedProperty(values)
         return if (rawValue != null)
             UnknownProperty.fromJsonString(rawValue)
         else
@@ -588,7 +587,7 @@ class AndroidEventTest {
         buildEvent(true) {
             url = URI("https://example.com")
         }.let { result ->
-            assertEquals("https://example.com", firstExtendedProperty(result, AndroidEvent.EXTNAME_URL))
+            assertEquals("https://example.com", firstExtendedProperty(result))
         }
     }
 
@@ -868,9 +867,7 @@ class AndroidEventTest {
         buildEvent(true) {
             alarms += VAlarm(Period.ofDays(-1))
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(1440, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(1440, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -879,9 +876,7 @@ class AndroidEventTest {
         buildEvent(true) {
             alarms += VAlarm(Duration.ofSeconds(-10))
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(0, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(0, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -891,9 +886,7 @@ class AndroidEventTest {
         buildEvent(true) {
             alarms += VAlarm(Duration.ofMinutes(10))
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(-10, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(-10, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -906,9 +899,7 @@ class AndroidEventTest {
                 trigger.parameters.add(Related.END)
             }
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(1320, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(1320, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -921,9 +912,7 @@ class AndroidEventTest {
                 trigger.parameters.add(Related.END)
             }
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(0, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(0, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -937,9 +926,7 @@ class AndroidEventTest {
                 trigger.parameters.add(Related.END)
             }
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(-130, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(-130, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -949,9 +936,7 @@ class AndroidEventTest {
             dtStart = DtStart(DateTime("20200621T120000", tzVienna))
             alarms += VAlarm(DateTime("20200621T110000", tzVienna))
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(60, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(60, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -961,9 +946,7 @@ class AndroidEventTest {
             dtStart = DtStart(DateTime("20200621T120000", tzVienna))
             alarms += VAlarm(DateTime("20200621T110000", tzShanghai))
         }.let { result ->
-            firstReminder(result)!!.let { reminder ->
-                assertEquals(420, reminder.getAsInteger(Reminders.MINUTES))
-            }
+            assertEquals(420, firstReminder(result)!!.getAsInteger(Reminders.MINUTES))
         }
     }
 
@@ -986,9 +969,7 @@ class AndroidEventTest {
         buildEvent(true) {
             attendees += Attendee("mailto:attendee1@example.com")
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals("attendee1@example.com", attendee.getAsString(Attendees.ATTENDEE_EMAIL))
-            }
+            assertEquals("attendee1@example.com", firstAttendee(result)!!.getAsString(Attendees.ATTENDEE_EMAIL))
         }
     }
 
@@ -1026,9 +1007,7 @@ class AndroidEventTest {
                 parameters.add(Cn("Sample Attendee"))
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals("Sample Attendee", attendee.getAsString(Attendees.ATTENDEE_NAME))
-            }
+            assertEquals("Sample Attendee", firstAttendee(result)!!.getAsString(Attendees.ATTENDEE_NAME))
         }
     }
 
@@ -1231,25 +1210,22 @@ class AndroidEventTest {
 
     @Test
     fun testBuildAttendee_Organizer() {
-        for (cuType in arrayOf(null, CuType.INDIVIDUAL, CuType.UNKNOWN, CuType.GROUP, CuType("x-custom-cutype")))
-            buildEvent(true) {
-                attendees += Attendee(URI("mailto", testAccount.name, null))
-            }.let { result ->
-                firstAttendee(result)!!.let { attendee ->
-                    assertEquals(testAccount.name, attendee.getAsString(Attendees.ATTENDEE_EMAIL))
-                    assertEquals(Attendees.TYPE_REQUIRED, attendee.getAsInteger(Attendees.ATTENDEE_TYPE))
-                    assertEquals(Attendees.RELATIONSHIP_ORGANIZER, attendee.getAsInteger(Attendees.ATTENDEE_RELATIONSHIP))
-                }
+        buildEvent(true) {
+            attendees += Attendee(URI("mailto", testAccount.name, null))
+        }.let { result ->
+            firstAttendee(result)!!.let { attendee ->
+                assertEquals(testAccount.name, attendee.getAsString(Attendees.ATTENDEE_EMAIL))
+                assertEquals(Attendees.TYPE_REQUIRED, attendee.getAsInteger(Attendees.ATTENDEE_TYPE))
+                assertEquals(Attendees.RELATIONSHIP_ORGANIZER, attendee.getAsInteger(Attendees.ATTENDEE_RELATIONSHIP))
             }
+        }
     }
     @Test
     fun testBuildAttendee_PartStat_None() {
         buildEvent(true) {
             attendees += Attendee("mailto:attendee@example.com")
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_INVITED, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_INVITED, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1260,9 +1236,7 @@ class AndroidEventTest {
                 parameters.add(PartStat.NEEDS_ACTION)
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_INVITED, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_INVITED, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1273,9 +1247,7 @@ class AndroidEventTest {
                 parameters.add(PartStat.ACCEPTED)
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_ACCEPTED, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_ACCEPTED, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1286,9 +1258,7 @@ class AndroidEventTest {
                 parameters.add(PartStat.DECLINED)
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_DECLINED, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_DECLINED, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1299,9 +1269,7 @@ class AndroidEventTest {
                 parameters.add(PartStat.TENTATIVE)
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_TENTATIVE, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_TENTATIVE, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1312,9 +1280,7 @@ class AndroidEventTest {
                 parameters.add(PartStat.DELEGATED)
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_NONE, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_NONE, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -1325,9 +1291,7 @@ class AndroidEventTest {
                 parameters.add(PartStat("X-WILL-ASK"))
             }
         }.let { result ->
-            firstAttendee(result)!!.let { attendee ->
-                assertEquals(Attendees.ATTENDEE_STATUS_INVITED, attendee.getAsInteger(Attendees.ATTENDEE_STATUS))
-            }
+            assertEquals(Attendees.ATTENDEE_STATUS_INVITED, firstAttendee(result)!!.getAsInteger(Attendees.ATTENDEE_STATUS))
         }
     }
 
@@ -2408,7 +2372,7 @@ class AndroidEventTest {
         event.dtStart = DtStart("20150502T120000Z")
         event.dtEnd = DtEnd("20150502T130000Z")
         event.organizer = Organizer(URI("mailto:organizer@example.com"))
-        val uri = TestEvent(calendar, event).add()
+        val uri = AndroidEvent(calendar, event, "update-event").add()
 
         // update test event in calendar
         val testEvent = calendar.findById(ContentUris.parseId(uri))
@@ -2442,7 +2406,7 @@ class AndroidEventTest {
             dtStart = DtStart(DateTime())
             color = Css3Color.silver
         }
-        val uri = TestEvent(calendar, event).add()
+        val uri = AndroidEvent(calendar, event, "reset-color").add()
         val id = ContentUris.parseId(uri)
 
         // verify that it has color
@@ -2465,7 +2429,7 @@ class AndroidEventTest {
         event.summary = "Sample event with STATUS"
         event.dtStart = DtStart("20150502T120000Z")
         event.dtEnd = DtEnd("20150502T130000Z")
-        val uri = TestEvent(calendar, event).add()
+        val uri = AndroidEvent(calendar, event, "update-status-from-null").add()
 
         // update test event in calendar
         val testEvent = calendar.findById(ContentUris.parseId(uri))
@@ -2495,7 +2459,7 @@ class AndroidEventTest {
         event.dtStart = DtStart("20150502T120000Z")
         event.dtEnd = DtEnd("20150502T130000Z")
         event.status = Status.VEVENT_CONFIRMED
-        val uri = TestEvent(calendar, event).add()
+        val uri = AndroidEvent(calendar, event, "update-status-to-null").add()
 
         // update test event in calendar
         val testEvent = calendar.findById(ContentUris.parseId(uri))
@@ -2528,7 +2492,7 @@ class AndroidEventTest {
         event.dtEnd = DtEnd("20150502T130000Z")
         for (i in 0 until 20)
             event.attendees += Attendee(URI("mailto:att$i@example.com"))
-        val uri = TestEvent(calendar, event).add()
+        val uri = AndroidEvent(calendar, event, "transaction").add()
 
         val testEvent = calendar.findById(ContentUris.parseId(uri))
         try {
@@ -2538,4 +2502,240 @@ class AndroidEventTest {
         }
     }
 
+
+    // companion object
+
+    @Test
+    fun testMarkEventAsDeleted() {
+        // Create event
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "A fine event"
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        // Delete event
+        AndroidEvent.markAsDeleted(provider, testAccount, localEvent.id!!)
+
+        // Get the status of whether the event is deleted
+        provider.query(
+            ContentUris.withAppendedId(Events.CONTENT_URI, localEvent.id!!).asSyncAdapter(testAccount),
+            arrayOf(Events.DELETED),
+            null,
+            null, null
+        )!!.use { cursor ->
+            cursor.moveToFirst()
+            assertEquals(1, cursor.getInt(0))
+        }
+    }
+
+
+    @Test
+    fun testNumDirectInstances_SingleInstance() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 1 instance"
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(1, AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumDirectInstances_Recurring() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 5 instances"
+            rRules.add(RRule("FREQ=DAILY;COUNT=5"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(5, AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumDirectInstances_Recurring_Endless() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event without end"
+            rRules.add(RRule("FREQ=DAILY"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertNull(AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    // flaky, needs InitCalendarProviderRule
+    fun testNumDirectInstances_Recurring_LateEnd() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 53 years"
+            rRules.add(RRule("FREQ=YEARLY;UNTIL=20740119T010203Z"))     // year 2074 is not supported by Android <11 Calendar Storage
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
+            assertEquals(52, AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+        else
+            assertNull(AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumDirectInstances_Recurring_ManyInstances() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 2 years"
+            rRules.add(RRule("FREQ=DAILY;UNTIL=20240120T010203Z"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+        val number = AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!)
+
+        // Some android versions (i.e. <=Q and S) return 365*2 instances (wrong, 365*2+1 => correct),
+        // but we are satisfied with either result for now
+        assertTrue(number == 365 * 2 || number == 365 * 2 + 1)
+    }
+
+    @Test
+    fun testNumDirectInstances_RecurringWithExdate() {
+        val event = Event().apply {
+            dtStart = DtStart(Date("20220120T010203Z"))
+            summary = "Event with 5 instances"
+            rRules.add(RRule("FREQ=DAILY;COUNT=5"))
+            exDates.add(ExDate(DateList("20220121T010203Z", Value.DATE_TIME)))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(4, AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumDirectInstances_RecurringWithExceptions() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 5 instances"
+            rRules.add(RRule("FREQ=DAILY;COUNT=5"))
+            exceptions.add(Event().apply {
+                recurrenceId = RecurrenceId("20220122T010203Z")
+                dtStart = DtStart("20220122T130203Z")
+                summary = "Exception on 3rd day"
+            })
+            exceptions.add(Event().apply {
+                recurrenceId = RecurrenceId("20220124T010203Z")
+                dtStart = DtStart("20220122T160203Z")
+                summary = "Exception on 5th day"
+            })
+        }
+        val localEvent = AndroidEvent(calendar, event, "filename.ics", null, null, 0)
+        localEvent.add()
+
+        assertEquals(5 - 2, AndroidEvent.numDirectInstances(provider, testAccount, localEvent.id!!))
+    }
+
+
+    @Test
+    fun testNumInstances_SingleInstance() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 1 instance"
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(1, AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumInstances_Recurring() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 5 instances"
+            rRules.add(RRule("FREQ=DAILY;COUNT=5"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(5, AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumInstances_Recurring_Endless() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with infinite instances"
+            rRules.add(RRule("FREQ=YEARLY"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertNull(AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumInstances_Recurring_LateEnd() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event over 22 years"
+            rRules.add(RRule("FREQ=YEARLY;UNTIL=20740119T010203Z"))     // year 2074 not supported by Android <11 Calendar Storage
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
+            assertEquals(52, AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+        else
+            assertNull(AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+    }
+
+    @Test
+    fun testNumInstances_Recurring_ManyInstances() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event over two years"
+            rRules.add(RRule("FREQ=DAILY;UNTIL=20240120T010203Z"))
+        }
+        val localEvent = AndroidEvent(calendar, event, null, null, null, 0)
+        localEvent.add()
+
+        assertEquals(
+            if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.Q)
+                365 * 2       // Android <10: does not include UNTIL (incorrect!)
+            else
+                365 * 2 + 1,  // Android ≥10: includes UNTIL (correct)
+            AndroidEvent.numInstances(provider, testAccount, localEvent.id!!)
+        )
+    }
+
+    @Test
+    fun testNumInstances_RecurringWithExceptions() {
+        val event = Event().apply {
+            dtStart = DtStart("20220120T010203Z")
+            summary = "Event with 6 instances"
+            rRules.add(RRule("FREQ=DAILY;COUNT=6"))
+            exceptions.add(Event().apply {
+                recurrenceId = RecurrenceId("20220122T010203Z")
+                dtStart = DtStart("20220122T130203Z")
+                summary = "Exception on 3rd day"
+            })
+            exceptions.add(Event().apply {
+                recurrenceId = RecurrenceId("20220124T010203Z")
+                dtStart = DtStart("20220122T160203Z")
+                summary = "Exception on 5th day"
+            })
+        }
+        val localEvent = AndroidEvent(calendar, event, "filename.ics", null, null, 0)
+        localEvent.add()
+
+        calendar.findById(localEvent.id!!)
+
+        assertEquals(6, AndroidEvent.numInstances(provider, testAccount, localEvent.id!!))
+    }
+
 }
\ No newline at end of file
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/DmfsStyleProvidersTaskTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/DmfsStyleProvidersTaskTest.kt
index 2eff0db3..9ddf2462 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/DmfsStyleProvidersTaskTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/DmfsStyleProvidersTaskTest.kt
@@ -7,7 +7,7 @@
 package at.bitfire.ical4android
 
 import androidx.test.platform.app.InstrumentationRegistry
-import at.bitfire.synctools.GrantPermissionOrSkipRule
+import at.bitfire.synctools.test.GrantPermissionOrSkipRule
 import org.junit.After
 import org.junit.Assert.assertNotNull
 import org.junit.Before
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/EventTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/EventTest.kt
index f2f4d725..0104df36 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/EventTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/EventTest.kt
@@ -6,6 +6,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.impl.testProdId
 import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateTime
@@ -76,7 +77,7 @@ class EventTest {
         e.alarms += VAlarm(Duration.ofMinutes(-30))
         e.attendees += Attendee("mailto:test@example.com")
         val baos = ByteArrayOutputStream()
-        e.write(baos)
+        e.write(baos, testProdId)
         val ical = baos.toString()
 
         assertTrue("BEGIN:VTIMEZONE.+BEGIN:STANDARD.+END:STANDARD.+END:VTIMEZONE".toRegex(RegexOption.DOT_MATCHES_ALL).containsMatchIn(ical))
@@ -141,7 +142,7 @@ class EventTest {
             )
         }
         val baos = ByteArrayOutputStream()
-        event.write(baos)
+        event.write(baos, testProdId)
         val iCal = baos.toString()
         assertTrue(iCal.contains("UID:test1\r\n"))
         assertTrue(iCal.contains("DTSTART;TZID=Europe/Berlin:20190117T083000\r\n"))
@@ -250,10 +251,10 @@ class EventTest {
         e.alarms += VAlarm(Duration.ofHours(-1))
 
         val os = ByteArrayOutputStream()
-        e.write(os)
+        e.write(os, testProdId)
         val raw = os.toString(Charsets.UTF_8.name())
 
-        assertTrue(raw.contains("PRODID:${ICalendar.prodId.value}"))
+        assertTrue(raw.contains("PRODID:${testProdId.value}"))
         assertTrue(raw.contains("UID:SAMPLEUID"))
         assertTrue(raw.contains("DTSTART;TZID=Europe/Berlin:20190101T100000"))
         assertTrue(raw.contains("DTSTAMP:"))
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxCollectionTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxCollectionTest.kt
index b863d3db..d6739f51 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxCollectionTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxCollectionTest.kt
@@ -11,8 +11,9 @@ import android.content.ContentProviderClient
 import android.content.ContentValues
 import androidx.test.platform.app.InstrumentationRegistry
 import at.bitfire.ical4android.impl.TestJtxCollection
+import at.bitfire.ical4android.impl.testProdId
 import at.bitfire.ical4android.util.MiscUtils.closeCompat
-import at.bitfire.synctools.GrantPermissionOrSkipRule
+import at.bitfire.synctools.test.GrantPermissionOrSkipRule
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.asSyncAdapter
 import junit.framework.TestCase.assertEquals
@@ -148,9 +149,10 @@ class JtxCollectionTest {
         client.insert(JtxContract.JtxICalObject.CONTENT_URI.asSyncAdapter(testAccount), cv1)
         client.insert(JtxContract.JtxICalObject.CONTENT_URI.asSyncAdapter(testAccount), cv2)
 
-        val ics = collections[0].getICSForCollection()
+        val ics = collections[0].getICSForCollection(testProdId)
         assertTrue(ics.contains(Regex("BEGIN:VCALENDAR(\\n*|\\r*|\\t*|.*)*END:VCALENDAR")))
-        assertTrue(ics.contains("PRODID:+//IDN bitfire.at//ical4android"))
+        System.err.println(ics)
+        assertTrue(ics.contains("PRODID:${testProdId.value}"))
         assertTrue(ics.contains("SUMMARY:summary"))
         assertTrue(ics.contains("SUMMARY:entry2"))
         assertTrue(ics.contains(Regex("BEGIN:VJOURNAL(\\n*|\\r*|\\t*|.*)*END:VJOURNAL")))
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxICalObjectTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxICalObjectTest.kt
index 73a1c980..ba892521 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxICalObjectTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/JtxICalObjectTest.kt
@@ -14,8 +14,9 @@ import android.os.ParcelFileDescriptor
 import androidx.core.content.pm.PackageInfoCompat
 import androidx.test.platform.app.InstrumentationRegistry
 import at.bitfire.ical4android.impl.TestJtxCollection
+import at.bitfire.ical4android.impl.testProdId
 import at.bitfire.ical4android.util.MiscUtils.closeCompat
-import at.bitfire.synctools.GrantPermissionOrSkipRule
+import at.bitfire.synctools.test.GrantPermissionOrSkipRule
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.JtxICalObject
 import at.techbee.jtx.JtxContract.JtxICalObject.Component
@@ -881,7 +882,7 @@ class JtxICalObjectTest {
 
         val os = ByteArrayOutputStream()
 
-        iCalObject[0].write(os)
+        iCalObject[0].write(os, testProdId)
 
         val iCalOut = ICalendar.fromReader(os.toByteArray().inputStream().reader())
 
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/TaskTest.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/TaskTest.kt
index d2d58da8..fcc8a6f2 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/TaskTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/TaskTest.kt
@@ -6,13 +6,13 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.impl.testProdId
 import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateList
 import net.fortuna.ical4j.model.DateTime
 import net.fortuna.ical4j.model.Parameter
 import net.fortuna.ical4j.model.TimeZone
-import net.fortuna.ical4j.model.TimeZoneRegistryFactory
 import net.fortuna.ical4j.model.component.VAlarm
 import net.fortuna.ical4j.model.parameter.RelType
 import net.fortuna.ical4j.model.parameter.Value
@@ -207,10 +207,10 @@ class TaskTest {
         t.alarms += alarm
 
         val os = ByteArrayOutputStream()
-        t.write(os)
+        t.write(os, testProdId)
         val raw = os.toString(Charsets.UTF_8.name())
 
-        assertTrue(raw.contains("PRODID:${t.prodId().value}"))
+        assertTrue(raw.contains("PRODID:${testProdId.value}"))
         assertTrue(raw.contains("UID:SAMPLEUID"))
         assertTrue(raw.contains("DTSTAMP:"))
         assertTrue(raw.contains("DTSTART;TZID=Europe/Berlin:20190101T100000"))
@@ -267,7 +267,7 @@ class TaskTest {
 
     private fun regenerate(t: Task): Task {
         val os = ByteArrayOutputStream()
-        t.write(os)
+        t.write(os, testProdId)
         return Task.tasksFromReader(InputStreamReader(ByteArrayInputStream(os.toByteArray()), Charsets.UTF_8)).first()
     }
     
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEventFactory.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/Constants.kt
similarity index 52%
rename from lib/src/main/kotlin/at/bitfire/ical4android/AndroidEventFactory.kt
rename to lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/Constants.kt
index eef6bc2a..6666d401 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEventFactory.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/Constants.kt
@@ -4,12 +4,8 @@
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.impl
 
-import android.content.ContentValues
+import net.fortuna.ical4j.model.property.ProdId
 
-interface AndroidEventFactory<out T: AndroidEvent> {
-
-    fun fromProvider(calendar: AndroidCalendar<AndroidEvent>, values: ContentValues): T
-
-}
\ No newline at end of file
+val testProdId = ProdId("bitfireAT/synctools test")
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestCalendar.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestCalendar.kt
index a834b333..6cb6864d 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestCalendar.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestCalendar.kt
@@ -18,7 +18,7 @@ class TestCalendar(
     account: Account,
     providerClient: ContentProviderClient,
     id: Long
-): AndroidCalendar<TestEvent>(account, providerClient, TestEvent.Factory, id) {
+) : AndroidCalendar(account, providerClient, id) {
 
     companion object {
         fun findOrCreate(account: Account, provider: ContentProviderClient): TestCalendar {
diff --git a/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestEvent.kt b/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestEvent.kt
deleted file mode 100644
index ce8c39db..00000000
--- a/lib/src/androidTest/kotlin/at/bitfire/ical4android/impl/TestEvent.kt
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * This file is part of bitfireAT/synctools which is released under GPLv3.
- * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
- * SPDX-License-Identifier: GPL-3.0-or-later
- */
-
-package at.bitfire.ical4android.impl
-
-import android.content.ContentValues
-import at.bitfire.ical4android.AndroidCalendar
-import at.bitfire.ical4android.AndroidEvent
-import at.bitfire.ical4android.AndroidEventFactory
-import at.bitfire.ical4android.Event
-import java.util.UUID
-
-class TestEvent: AndroidEvent {
-
-    constructor(calendar: AndroidCalendar<AndroidEvent>, values: ContentValues)
-        : super(calendar, values)
-
-    constructor(calendar: TestCalendar, event: Event)
-            : super(calendar, event, UUID.randomUUID().toString(), null, null, 0)
-
-
-    object Factory: AndroidEventFactory<TestEvent> {
-        override fun fromProvider(calendar: AndroidCalendar<AndroidEvent>, values: ContentValues) =
-                TestEvent(calendar, values)
-    }
-
-}
diff --git a/lib/src/androidTest/kotlin/at/bitfire/synctools/storage/JtxBatchOperationTest.kt b/lib/src/androidTest/kotlin/at/bitfire/synctools/storage/JtxBatchOperationTest.kt
index 0a21e0dd..39abe136 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/synctools/storage/JtxBatchOperationTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/synctools/storage/JtxBatchOperationTest.kt
@@ -16,7 +16,7 @@ import at.bitfire.ical4android.JtxICalObject
 import at.bitfire.ical4android.TaskProvider
 import at.bitfire.ical4android.util.MiscUtils.asSyncAdapter
 import at.bitfire.ical4android.util.MiscUtils.closeCompat
-import at.bitfire.synctools.GrantPermissionOrSkipRule
+import at.bitfire.synctools.test.GrantPermissionOrSkipRule
 import at.techbee.jtx.JtxContract
 import io.mockk.mockk
 import org.junit.After
diff --git a/lib/src/androidTest/kotlin/at/bitfire/vcard4android/AndroidContactTest.kt b/lib/src/androidTest/kotlin/at/bitfire/vcard4android/AndroidContactTest.kt
index b3474753..2e82630b 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/vcard4android/AndroidContactTest.kt
+++ b/lib/src/androidTest/kotlin/at/bitfire/vcard4android/AndroidContactTest.kt
@@ -17,14 +17,20 @@ import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
 import at.bitfire.synctools.storage.LocalStorageException
 import at.bitfire.vcard4android.impl.TestAddressBook
+import at.bitfire.vcard4android.impl.testProductId
 import at.bitfire.vcard4android.property.XAbDate
 import ezvcard.VCardVersion
 import ezvcard.property.Address
 import ezvcard.property.Birthday
 import ezvcard.property.Email
 import ezvcard.util.PartialDate
-import org.junit.*
-import org.junit.Assert.*
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
+import org.junit.BeforeClass
+import org.junit.ClassRule
+import org.junit.Test
 import java.io.ByteArrayOutputStream
 import java.io.StringReader
 import java.time.LocalDate
@@ -206,8 +212,8 @@ class AndroidContactTest {
          * So, ADR value components may contain DQUOTE (0x22) and don't have to be encoded as defined in RFC 6868 */
 
         val os = ByteArrayOutputStream()
-        contact.writeVCard(VCardVersion.V4_0, os)
+        contact.writeVCard(VCardVersion.V4_0, os, testProductId)
         assertTrue(os.toString().contains("ADR;LABEL=My ^'Label^'\\nLine 2:;;Street \"Address\";;;;"))
     }
 
-}
+}
\ No newline at end of file
diff --git a/lib/src/androidTest/kotlin/at/bitfire/vcard4android/impl/Constants.kt b/lib/src/androidTest/kotlin/at/bitfire/vcard4android/impl/Constants.kt
new file mode 100644
index 00000000..0b881e44
--- /dev/null
+++ b/lib/src/androidTest/kotlin/at/bitfire/vcard4android/impl/Constants.kt
@@ -0,0 +1,9 @@
+/*
+ * This file is part of bitfireAT/synctools which is released under GPLv3.
+ * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package at.bitfire.vcard4android.impl
+
+val testProductId = "bitfireAT/synctools test"
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendar.kt b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendar.kt
index 05f820ad..77753a08 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendar.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendar.kt
@@ -31,10 +31,9 @@ import java.util.logging.Logger
  * Communicates with the Android Contacts Provider which uses an SQLite
  * database to store the events.
  */
-open class AndroidCalendar<out T : AndroidEvent>(
+open class AndroidCalendar(
     val account: Account,
     val provider: ContentProviderClient,
-    val eventFactory: AndroidEventFactory<T>,
 
     /** the calendar ID ([Calendars._ID]) **/
     val id: Long
@@ -100,14 +99,14 @@ open class AndroidCalendar<out T : AndroidEvent>(
      * @param _whereArgs arguments for selection
      * @return events from this calendar which match the selection
      */
-    fun queryEvents(_where: String? = null, _whereArgs: Array<String>? = null): List<T> {
+    fun queryEvents(_where: String? = null, _whereArgs: Array<String>? = null): List<AndroidEvent> {
         val where = "(${_where ?: "1"}) AND " + Events.CALENDAR_ID + "=?"
         val whereArgs = (_whereArgs ?: arrayOf()) + id.toString()
 
-        val events = LinkedList<T>()
+        val events = LinkedList<AndroidEvent>()
         provider.query(Events.CONTENT_URI.asSyncAdapter(account), null, where, whereArgs, null)?.use { cursor ->
             while (cursor.moveToNext())
-                events += eventFactory.fromProvider(this, cursor.toValues())
+                events += AndroidEvent(this, cursor.toValues())
         }
         return events
     }
@@ -216,7 +215,12 @@ open class AndroidCalendar<out T : AndroidEvent>(
             provider.delete(Colors.CONTENT_URI.asSyncAdapter(account), null, null)
         }
 
-        fun<T: AndroidCalendar<AndroidEvent>> findByID(account: Account, provider: ContentProviderClient, factory: AndroidCalendarFactory<T>, id: Long): T {
+        fun <T : AndroidCalendar> findByID(
+            account: Account,
+            provider: ContentProviderClient,
+            factory: AndroidCalendarFactory<T>,
+            id: Long
+        ): T {
             val iterCalendars = CalendarEntity.newEntityIterator(
                 provider.query(ContentUris.withAppendedId(CalendarEntity.CONTENT_URI, id).asSyncAdapter(account), null, null, null, null)
             )
@@ -233,7 +237,13 @@ open class AndroidCalendar<out T : AndroidEvent>(
             throw FileNotFoundException()
         }
 
-        fun<T: AndroidCalendar<AndroidEvent>> find(account: Account, provider: ContentProviderClient, factory: AndroidCalendarFactory<T>, where: String?, whereArgs: Array<String>?): List<T> {
+        fun <T : AndroidCalendar> find(
+            account: Account,
+            provider: ContentProviderClient,
+            factory: AndroidCalendarFactory<T>,
+            where: String?,
+            whereArgs: Array<String>?
+        ): List<T> {
             val iterCalendars = CalendarEntity.newEntityIterator(
                 provider.query(CalendarEntity.CONTENT_URI.asSyncAdapter(account), null, where, whereArgs, null)
             )
@@ -253,4 +263,11 @@ open class AndroidCalendar<out T : AndroidEvent>(
 
     }
 
+
+    // default factory (will be removed as soon as AndroidCalendar is not open anymore)
+    object Factory : AndroidCalendarFactory<AndroidCalendar> {
+        override fun newInstance(account: Account, provider: ContentProviderClient, id: Long) =
+            AndroidCalendar(account, provider, id)
+    }
+
 }
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendarFactory.kt b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendarFactory.kt
index 4ae5e51c..a043421e 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendarFactory.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidCalendarFactory.kt
@@ -9,7 +9,7 @@ package at.bitfire.ical4android
 import android.accounts.Account
 import android.content.ContentProviderClient
 
-interface AndroidCalendarFactory<out T: AndroidCalendar<AndroidEvent>> {
+interface AndroidCalendarFactory<out T : AndroidCalendar> {
 
     fun newInstance(account: Account, provider: ContentProviderClient, id: Long): T
 
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEvent.kt b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEvent.kt
index 85b86ea7..af4cbcec 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEvent.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/AndroidEvent.kt
@@ -6,12 +6,15 @@
 
 package at.bitfire.ical4android
 
+import android.accounts.Account
+import android.content.ContentProviderClient
 import android.content.ContentResolver
 import android.content.ContentUris
 import android.content.ContentValues
 import android.content.EntityIterator
 import android.net.Uri
 import android.os.RemoteException
+import android.provider.CalendarContract
 import android.provider.CalendarContract.Attendees
 import android.provider.CalendarContract.Colors
 import android.provider.CalendarContract.Events
@@ -19,8 +22,9 @@ import android.provider.CalendarContract.EventsEntity
 import android.provider.CalendarContract.ExtendedProperties
 import android.provider.CalendarContract.Reminders
 import android.util.Patterns
-import androidx.annotation.CallSuper
+import androidx.core.content.contentValuesOf
 import at.bitfire.ical4android.AndroidEvent.Companion.CATEGORIES_SEPARATOR
+import at.bitfire.ical4android.AndroidEvent.Companion.numInstances
 import at.bitfire.ical4android.util.AndroidTimeUtils
 import at.bitfire.ical4android.util.DateUtils
 import at.bitfire.ical4android.util.MiscUtils.asSyncAdapter
@@ -56,6 +60,7 @@ import net.fortuna.ical4j.model.property.DtEnd
 import net.fortuna.ical4j.model.property.DtStart
 import net.fortuna.ical4j.model.property.ExDate
 import net.fortuna.ical4j.model.property.ExRule
+import net.fortuna.ical4j.model.property.LastModified
 import net.fortuna.ical4j.model.property.Organizer
 import net.fortuna.ical4j.model.property.RDate
 import net.fortuna.ical4j.model.property.RRule
@@ -84,44 +89,56 @@ import java.util.logging.Logger
  * Important: To use recurrence exceptions, you MUST set _SYNC_ID and ORIGINAL_SYNC_ID
  * in populateEvent() / buildEvent. Setting _ID and ORIGINAL_ID is not sufficient.
  */
-open class AndroidEvent(
-    val calendar: AndroidCalendar<AndroidEvent>
+class AndroidEvent(
+    val calendar: AndroidCalendar
 ) {
 
-    protected val logger: Logger by lazy { Logger.getLogger(AndroidEvent::class.java.name) }
+    private val logger: Logger
+        get() = Logger.getLogger(javaClass.name)
 
     var id: Long? = null
-        protected set
+        private set
 
-    open var syncId: String? = null
+    var syncId: String? = null
 
     var eTag: String? = null
     var scheduleTag: String? = null
     var flags: Int = 0
+    var lastModified: Long = 0L
 
     /**
      * Creates a new object from an event which already exists in the calendar storage.
      *
      * @param values database row with all columns, as returned by the calendar provider
      */
-    constructor(calendar: AndroidCalendar<*>, values: ContentValues) : this(calendar) {
+    constructor(calendar: AndroidCalendar, values: ContentValues) : this(calendar) {
         this.id = values.getAsLong(Events._ID)
         this.syncId = values.getAsString(Events._SYNC_ID)
         this.eTag = values.getAsString(COLUMN_ETAG)
         this.scheduleTag = values.getAsString(COLUMN_SCHEDULE_TAG)
         this.flags = values.getAsInteger(COLUMN_FLAGS) ?: 0
+        this.lastModified = values.getAsLong(COLUMN_LAST_MODIFIED) ?: 0L
     }
 
     /**
      * Creates a new object from an event which doesn't exist in the calendar storage yet.
+     *
      * @param event event that can be saved into the calendar storage
      */
-    constructor(calendar: AndroidCalendar<*>, event: Event, syncId: String?, eTag: String?, scheduleTag: String?, flags: Int) : this(calendar) {
+    constructor(
+        calendar: AndroidCalendar,
+        event: Event,
+        syncId: String?,
+        eTag: String? = null,
+        scheduleTag: String? = null,
+        flags: Int = 0
+    ) : this(calendar) {
         this.event = event
         this.syncId = syncId
         this.eTag = eTag
         this.scheduleTag = scheduleTag
         this.flags = flags
+        this.lastModified = event.lastModified?.dateTime?.time ?: 0L
     }
 
     private var _event: Event? = null
@@ -167,7 +184,7 @@ open class AndroidEvent(
                     for (subValue in e.subValues) {
                         val subValues = subValue.values.removeBlankStrings()
                         when (subValue.uri) {
-                            Attendees.CONTENT_URI -> populateAttendee(subValues, isOrganizer)
+                            Attendees.CONTENT_URI -> populateAttendee(subValues)
                             Reminders.CONTENT_URI -> populateReminder(subValues)
                             ExtendedProperties.CONTENT_URI -> populateExtended(subValues)
                         }
@@ -193,7 +210,7 @@ open class AndroidEvent(
      *
      * @param row values of an [Events] row, as returned by the calendar provider
      */
-    protected fun populateEvent(row: ContentValues, groupScheduled: Boolean) {
+    private fun populateEvent(row: ContentValues, groupScheduled: Boolean) {
         logger.log(Level.FINE, "Read event entity from calender provider", row)
         val event = requireNotNull(event)
 
@@ -318,6 +335,9 @@ open class AndroidEvent(
         event.uid = row.getAsString(Events.UID_2445)
         event.sequence = row.getAsInteger(COLUMN_SEQUENCE)
         event.isOrganizer = row.getAsBoolean(Events.IS_ORGANIZER)
+        event.lastModified = row.getAsLong(COLUMN_LAST_MODIFIED)?.let { time ->
+            LastModified(DateTime(time))
+        }
 
         event.summary = row.getAsString(Events.TITLE)
         event.location = row.getAsString(Events.EVENT_LOCATION)
@@ -385,7 +405,7 @@ open class AndroidEvent(
         }
     }
 
-    protected open fun populateAttendee(row: ContentValues, isOrganizer: Boolean) {
+    private fun populateAttendee(row: ContentValues) {
         logger.log(Level.FINE, "Read event attendee from calender provider", row)
 
         try {
@@ -426,7 +446,7 @@ open class AndroidEvent(
         }
     }
 
-    protected open fun populateReminder(row: ContentValues) {
+    private fun populateReminder(row: ContentValues) {
         logger.log(Level.FINE, "Read event reminder from calender provider", row)
         val event = requireNotNull(event)
 
@@ -460,7 +480,7 @@ open class AndroidEvent(
         event.alarms += alarm
     }
 
-    protected open fun populateExtended(row: ContentValues) {
+    private fun populateExtended(row: ContentValues) {
         val name = row.getAsString(ExtendedProperties.NAME)
         val rawValue = row.getAsString(ExtendedProperties.VALUE)
         logger.log(Level.FINE, "Read extended property from calender provider", arrayOf(name, rawValue))
@@ -491,7 +511,7 @@ open class AndroidEvent(
         }
     }
 
-    protected open fun populateExceptions() {
+    private fun populateExceptions() {
         requireNotNull(id)
         val event = requireNotNull(event)
 
@@ -501,7 +521,7 @@ open class AndroidEvent(
             while (c.moveToNext()) {
                 val values = c.toValues(true)
                 try {
-                    val exception = calendar.eventFactory.fromProvider(calendar, values)
+                    val exception = AndroidEvent(calendar, values)
                     val exceptionEvent = exception.event!!
                     val recurrenceId = exceptionEvent.recurrenceId!!
 
@@ -753,7 +773,7 @@ open class AndroidEvent(
         return batch.commit()
     }
 
-    protected fun deleteExceptions(batch: CalendarBatchOperation) {
+    private fun deleteExceptions(batch: CalendarBatchOperation) {
         val existingId = requireNotNull(id)
         batch += CpoBuilder
             .newDelete(Events.CONTENT_URI.asSyncAdapter(calendar.account))
@@ -770,7 +790,7 @@ open class AndroidEvent(
      * @param recurrence   event to be used as data source; *null*: use this AndroidEvent's main [event] as source
      * @param builder      data row builder to be used
      */
-    protected fun buildEvent(recurrence: Event?, builder: CpoBuilder) {
+    private fun buildEvent(recurrence: Event?, builder: CpoBuilder) {
         val event = recurrence ?: requireNotNull(event)
 
         val dtStart = event.dtStart ?: throw InvalidCalendarException("Events must have DTSTART")
@@ -800,6 +820,7 @@ open class AndroidEvent(
             builder.withValue(Events._SYNC_ID, syncId)
                 .withValue(COLUMN_ETAG, eTag)
                 .withValue(COLUMN_SCHEDULE_TAG, scheduleTag)
+                .withValue(COLUMN_LAST_MODIFIED, lastModified)
         else
             builder.withValue(Events.ORIGINAL_SYNC_ID, syncId)
 
@@ -1003,7 +1024,7 @@ open class AndroidEvent(
                 })
     }
 
-    protected open fun insertReminder(batch: CalendarBatchOperation, idxEvent: Int?, alarm: VAlarm) {
+    private fun insertReminder(batch: CalendarBatchOperation, idxEvent: Int?, alarm: VAlarm) {
         val builder = CpoBuilder
                 .newInsert(Reminders.CONTENT_URI.asSyncAdapter(calendar.account))
                 .withEventId(Reminders.EVENT_ID, idxEvent)
@@ -1025,7 +1046,7 @@ open class AndroidEvent(
         batch += builder
     }
 
-    protected open fun insertAttendee(batch: CalendarBatchOperation, idxEvent: Int?, attendee: Attendee, organizer: String) {
+    private fun insertAttendee(batch: CalendarBatchOperation, idxEvent: Int?, attendee: Attendee, organizer: String) {
         val builder = CpoBuilder
                 .newInsert(Attendees.CONTENT_URI.asSyncAdapter(calendar.account))
                 .withEventId(Attendees.EVENT_ID, idxEvent)
@@ -1062,7 +1083,7 @@ open class AndroidEvent(
         batch += builder
     }
 
-    protected open fun insertExtendedProperty(batch: CalendarBatchOperation, idxEvent: Int?, name: String, value: String) {
+    private fun insertExtendedProperty(batch: CalendarBatchOperation, idxEvent: Int?, name: String, value: String) {
         val builder = CpoBuilder
             .newInsert(ExtendedProperties.CONTENT_URI.asSyncAdapter(calendar.account))
             .withEventId(ExtendedProperties.EVENT_ID, idxEvent)
@@ -1071,7 +1092,7 @@ open class AndroidEvent(
         batch += builder
     }
 
-    protected open fun insertCategories(batch: CalendarBatchOperation, idxEvent: Int?) {
+    private fun insertCategories(batch: CalendarBatchOperation, idxEvent: Int?) {
         val rawCategories = event!!.categories      // concatenate, separate by backslash
                 .joinToString(CATEGORIES_SEPARATOR.toString()) { category ->
                     // drop occurrences of CATEGORIES_SEPARATOR in category names
@@ -1080,7 +1101,7 @@ open class AndroidEvent(
         insertExtendedProperty(batch, idxEvent, EXTNAME_CATEGORIES, rawCategories)
     }
 
-    protected open fun insertUnknownProperty(batch: CalendarBatchOperation, idxEvent: Int?, property: Property) {
+    private fun insertUnknownProperty(batch: CalendarBatchOperation, idxEvent: Int?, property: Property) {
         if (property.value == null) {
             logger.warning("Ignoring unknown property with null value")
             return
@@ -1112,7 +1133,7 @@ open class AndroidEvent(
     }
 
 
-    protected fun CpoBuilder.withEventId(column: String, idxEvent: Int?): CpoBuilder {
+    private fun CpoBuilder.withEventId(column: String, idxEvent: Int?): CpoBuilder {
         if (idxEvent != null)
             withValueBackReference(column, idxEvent)
         else
@@ -1121,12 +1142,11 @@ open class AndroidEvent(
     }
 
 
-    protected fun eventSyncURI(): Uri {
+    private fun eventSyncURI(): Uri {
         val id = requireNotNull(id)
         return ContentUris.withAppendedId(Events.CONTENT_URI, id).asSyncAdapter(calendar.account)
     }
 
-    @CallSuper
     override fun toString(): String = "AndroidEvent(calendar=$calendar, id=$id, event=$_event)"
 
 
@@ -1154,6 +1174,11 @@ open class AndroidEvent(
          */
         const val COLUMN_SCHEDULE_TAG = Events.SYNC_DATA4
 
+        /**
+         * Custom sync column to store the last modified value of an event.
+         */
+        const val COLUMN_LAST_MODIFIED = Events.SYNC_DATA5
+
         /**
          * VEVENT CATEGORIES are stored as an extended property with this [ExtendedProperties.NAME].
          *
@@ -1180,6 +1205,107 @@ open class AndroidEvent(
          */
         const val EXTNAME_URL = ContentResolver.CURSOR_ITEM_BASE_TYPE + "/vnd.ical4android.url"
 
+
+        // helpers
+
+        /**
+         * Marks the event as deleted
+         * @param eventID
+         */
+        fun markAsDeleted(provider: ContentProviderClient, account: Account, eventID: Long) {
+            provider.update(
+                ContentUris.withAppendedId(
+                    Events.CONTENT_URI,
+                    eventID
+                ).asSyncAdapter(account),
+                contentValuesOf(Events.DELETED to 1),
+                null, null
+            )
+        }
+
+        /**
+         * Finds the amount of direct instances this event has (without exceptions); used by [numInstances]
+         * to find the number of instances of exceptions.
+         *
+         * The number of returned instances may vary with the Android version.
+         *
+         * @return number of direct event instances (not counting instances of exceptions); *null* if
+         * the number can't be determined or if the event has no last date (recurring event without last instance)
+         */
+        fun numDirectInstances(provider: ContentProviderClient, account: Account, eventID: Long): Int? {
+            // query event to get first and last instance
+            var first: Long? = null
+            var last: Long? = null
+            provider.query(
+                ContentUris.withAppendedId(
+                    Events.CONTENT_URI,
+                    eventID
+                ),
+                arrayOf(Events.DTSTART, Events.LAST_DATE), null, null, null
+            )?.use { cursor ->
+                cursor.moveToNext()
+                if (!cursor.isNull(0))
+                    first = cursor.getLong(0)
+                if (!cursor.isNull(1))
+                    last = cursor.getLong(1)
+            }
+            // if this event doesn't have a last occurence, it's endless and always has instances
+            if (first == null || last == null)
+                return null
+
+            /* We can't use Long.MIN_VALUE and Long.MAX_VALUE because Android generates the instances
+             on the fly and it doesn't accept those values. So we use the first/last actual occurence
+             of the event (calculated by Android). */
+            val instancesUri = CalendarContract.Instances.CONTENT_URI.asSyncAdapter(account)
+                .buildUpon()
+                .appendPath(first.toString())       // begin timestamp
+                .appendPath(last.toString())        // end timestamp
+                .build()
+
+            var numInstances = 0
+            provider.query(
+                instancesUri, null,
+                "${CalendarContract.Instances.EVENT_ID}=?", arrayOf(eventID.toString()),
+                null
+            )?.use { cursor ->
+                numInstances += cursor.count
+            }
+            return numInstances
+        }
+
+        /**
+         * Finds the total number of instances this event has (including instances of exceptions)
+         *
+         * The number of returned instances may vary with the Android version.
+         *
+         * @return number of direct event instances (not counting instances of exceptions); *null* if
+         * the number can't be determined or if the event has no last date (recurring event without last instance)
+         */
+        fun numInstances(provider: ContentProviderClient, account: Account, eventID: Long): Int? {
+            // num instances of the main event
+            var numInstances = numDirectInstances(provider, account, eventID) ?: return null
+
+            // add the number of instances of every main event's exception
+            provider.query(
+                Events.CONTENT_URI,
+                arrayOf(Events._ID),
+                "${Events.ORIGINAL_ID}=?", // get exception events of the main event
+                arrayOf("$eventID"), null
+            )?.use { exceptionsEventCursor ->
+                while (exceptionsEventCursor.moveToNext()) {
+                    val exceptionEventID = exceptionsEventCursor.getLong(0)
+                    val exceptionInstances = numDirectInstances(provider, account, exceptionEventID)
+
+                    if (exceptionInstances == null)
+                    // number of instances of exception can't be determined; so the total number of instances is also unclear
+                        return null
+
+                    numInstances += exceptionInstances
+                }
+            }
+            return numInstances
+        }
+
     }
 
 }
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/Event.kt b/lib/src/main/kotlin/at/bitfire/ical4android/Event.kt
index ec12145b..f8a3c372 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/Event.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/Event.kt
@@ -97,10 +97,16 @@ data class Event(
     val unknownProperties: LinkedList<Property> = LinkedList()
 ) : ICalendar() {
 
-    fun write(os: OutputStream) {
+    /**
+     * Generates an iCalendar from the Event.
+     *
+     * @param os        stream that the iCalendar is written to
+     * @param prodId    `PRODID` that identifies the app
+     */
+    fun write(os: OutputStream, prodId: ProdId) {
         val ical = Calendar()
         ical.properties += Version.VERSION_2_0
-        ical.properties += prodId()
+        ical.properties += prodId.withUserAgents(userAgents)
 
         val dtStart = dtStart ?: throw InvalidCalendarException("Won't generate event without start time")
 
@@ -374,4 +380,5 @@ data class Event(
             return e
         }
     }
+
 }
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/ICalendar.kt b/lib/src/main/kotlin/at/bitfire/ical4android/ICalendar.kt
index a8f4b1cc..7c9a51c5 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/ICalendar.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/ICalendar.kt
@@ -56,20 +56,29 @@ open class ICalendar {
             get() = Logger.getLogger(ICalendar::class.java.name)
 
         // known iCalendar properties
+
         const val CALENDAR_NAME = "X-WR-CALNAME"
         const val CALENDAR_COLOR = "X-APPLE-CALENDAR-COLOR"
 
+
+        // PRODID generation
+
         /**
-         * Default PRODID used when generating iCalendars. If you want another value, set it
-         * statically before writing the first iCalendar.
+         * Extends the given `PRODID` with the user agents (typically calendar app name and version).
+         * This way the `PRODID` does not only identify the app that actually produces the iCalendar,
+         * but also the used front-end app, which may be helpful when debugging the iCalendar.
+         *
+         * @param userAgents    list of involved user agents
+         *                      (preferably in `package name/version` format, for instance `com.example.mycalendar/1.0`)
+         *
+         * @return original `PRODID` with user agents in parentheses
          */
-        var prodId = ProdId("+//IDN bitfire.at//ical4android")
-
-        fun prodId(userAgents: List<String>): ProdId =
+        fun ProdId.withUserAgents(userAgents: List<String>) =
             if (userAgents.isEmpty())
-                prodId
+                this
             else
-                ProdId(prodId.value + " (" + userAgents.joinToString(",") + ")")
+                ProdId(value + " (${userAgents.joinToString(", ")})")
+
 
         // parser
 
@@ -373,6 +382,4 @@ open class ICalendar {
         uid = UUID.randomUUID().toString()
     }
 
-    fun prodId(): ProdId = prodId(userAgents)
-
 }
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/JtxCollection.kt b/lib/src/main/kotlin/at/bitfire/ical4android/JtxCollection.kt
index 9f12ba9b..0d2f54a2 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/JtxCollection.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/JtxCollection.kt
@@ -19,6 +19,7 @@ import at.techbee.jtx.JtxContract.asSyncAdapter
 import net.fortuna.ical4j.model.Calendar
 import net.fortuna.ical4j.model.component.VJournal
 import net.fortuna.ical4j.model.component.VToDo
+import net.fortuna.ical4j.model.property.ProdId
 import net.fortuna.ical4j.model.property.Version
 import java.util.LinkedList
 import java.util.logging.Level
@@ -243,9 +244,11 @@ open class JtxCollection<out T: JtxICalObject>(val account: Account,
 
 
     /**
+     * @param prodId    `PRODID` that identifies the app
+     *
      * @return a string with all JtxICalObjects within the collection as iCalendar
      */
-    fun getICSForCollection(): String {
+    fun getICSForCollection(prodId: ProdId): String {
         client.query(
             JtxContract.JtxICalObject.CONTENT_URI.asSyncAdapter(account),
             null,
@@ -257,12 +260,12 @@ open class JtxCollection<out T: JtxICalObject>(val account: Account,
 
             val ical = Calendar()
             ical.properties += Version.VERSION_2_0
-            ical.properties += ICalendar.prodId
+            ical.properties += prodId
 
             while (cursor?.moveToNext() == true) {
                 val jtxIcalObject = JtxICalObject(this)
                 jtxIcalObject.populateFromContentValues(cursor.toValues())
-                val singleICS = jtxIcalObject.getICalendarFormat()
+                val singleICS = jtxIcalObject.getICalendarFormat(prodId)
                 singleICS?.components?.forEach { component ->
                     if(component is VToDo || component is VJournal)
                         ical.components += component
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/JtxICalObject.kt b/lib/src/main/kotlin/at/bitfire/ical4android/JtxICalObject.kt
index 40f0ead7..916421af 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/JtxICalObject.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/JtxICalObject.kt
@@ -12,6 +12,7 @@ import android.net.ParseException
 import android.net.Uri
 import android.os.ParcelFileDescriptor
 import android.util.Base64
+import at.bitfire.ical4android.ICalendar.Companion.withUserAgents
 import at.bitfire.ical4android.util.MiscUtils.toValues
 import at.bitfire.synctools.storage.BatchOperation
 import at.bitfire.synctools.storage.JtxBatchOperation
@@ -629,12 +630,15 @@ open class JtxICalObject(
 
     /**
      * Takes the current JtxICalObject and transforms it to a Calendar (ical4j)
+     *
+     * @param prodId    `PRODID` that identifies the app
+     *
      * @return The current JtxICalObject transformed into a ical4j Calendar
      */
-    fun getICalendarFormat(): Calendar? {
+    fun getICalendarFormat(prodId: ProdId): Calendar? {
         val ical = Calendar()
         ical.properties += Version.VERSION_2_0
-        ical.properties += ICalendar.prodId(listOf(TaskProvider.ProviderName.JtxBoard.packageName))
+        ical.properties += prodId.withUserAgents(listOf(TaskProvider.ProviderName.JtxBoard.packageName))
 
         val calComponent = when (component) {
             JtxContract.JtxICalObject.Component.VTODO.name -> VToDo(true /* generates DTSTAMP */)
@@ -731,10 +735,12 @@ open class JtxICalObject(
 
     /**
      * Takes the current JtxICalObject, transforms it to an iCalendar and writes it in an OutputStream
+     *
      * @param [os] OutputStream where iCalendar should be written to
+     * @param prodId    `PRODID` that identifies the app
      */
-    fun write(os: OutputStream) {
-        CalendarOutputter(false).output(this.getICalendarFormat(), os)
+    fun write(os: OutputStream, prodId: ProdId) {
+        CalendarOutputter(false).output(this.getICalendarFormat(prodId), os)
     }
 
     /**
diff --git a/lib/src/main/kotlin/at/bitfire/ical4android/Task.kt b/lib/src/main/kotlin/at/bitfire/ical4android/Task.kt
index 40638860..6274904a 100644
--- a/lib/src/main/kotlin/at/bitfire/ical4android/Task.kt
+++ b/lib/src/main/kotlin/at/bitfire/ical4android/Task.kt
@@ -194,10 +194,16 @@ data class Task(
     }
 
 
-    fun write(os: OutputStream) {
+    /**
+     * Generates an iCalendar from the Task.
+     *
+     * @param os        stream that the iCalendar is written to
+     * @param prodId    `PRODID` that identifies the app
+     */
+    fun write(os: OutputStream, prodId: ProdId) {
         val ical = Calendar()
         ical.properties += Version.VERSION_2_0
-        ical.properties += prodId()
+        ical.properties += prodId.withUserAgents(userAgents)
 
         val vTodo = VToDo(true /* generates DTSTAMP */)
         ical.components += vTodo
diff --git a/lib/src/androidTest/kotlin/at/bitfire/synctools/GrantPermissionOrSkipRule.kt b/lib/src/main/kotlin/at/bitfire/synctools/test/GrantPermissionOrSkipRule.kt
similarity index 97%
rename from lib/src/androidTest/kotlin/at/bitfire/synctools/GrantPermissionOrSkipRule.kt
rename to lib/src/main/kotlin/at/bitfire/synctools/test/GrantPermissionOrSkipRule.kt
index ce834ea0..584acd7a 100644
--- a/lib/src/androidTest/kotlin/at/bitfire/synctools/GrantPermissionOrSkipRule.kt
+++ b/lib/src/main/kotlin/at/bitfire/synctools/test/GrantPermissionOrSkipRule.kt
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
 
-package at.bitfire.synctools
+package at.bitfire.synctools.test
 
 import androidx.test.rule.GrantPermissionRule
 import org.junit.Assume
diff --git a/lib/src/main/kotlin/at/bitfire/synctools/test/InitCalendarProviderRule.kt b/lib/src/main/kotlin/at/bitfire/synctools/test/InitCalendarProviderRule.kt
new file mode 100644
index 00000000..206a078c
--- /dev/null
+++ b/lib/src/main/kotlin/at/bitfire/synctools/test/InitCalendarProviderRule.kt
@@ -0,0 +1,122 @@
+/*
+ * This file is part of bitfireAT/synctools which is released under GPLv3.
+ * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package at.bitfire.synctools.test
+
+import android.Manifest
+import android.accounts.Account
+import android.content.ContentProviderClient
+import android.content.ContentUris
+import android.content.ContentValues
+import android.os.Build
+import android.provider.CalendarContract
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.rule.GrantPermissionRule
+import at.bitfire.ical4android.AndroidCalendar
+import at.bitfire.ical4android.AndroidEvent
+import at.bitfire.ical4android.Event
+import net.fortuna.ical4j.model.property.DtStart
+import net.fortuna.ical4j.model.property.RRule
+import org.junit.Assert
+import org.junit.rules.ExternalResource
+import org.junit.rules.RuleChain
+import java.util.logging.Logger
+
+/**
+ * JUnit ClassRule which initializes the AOSP CalendarProvider.
+ *
+ * It seems that the calendar provider unfortunately forgets the very first requests when it is used the very first time,
+ * maybe by some wrongly synchronized database initialization. So things like querying the instances
+ * fails in this case.
+ *
+ * So this rule is needed to allow tests which need the calendar provider to succeed even when the calendar provider
+ * is used the very first time (especially in CI tests / a fresh emulator).
+ */
+class InitCalendarProviderRule private constructor() : ExternalResource() {
+
+    companion object {
+
+        private var isInitialized = false
+        private val logger = Logger.getLogger(InitCalendarProviderRule::javaClass.name)
+
+        fun getInstance(): RuleChain = RuleChain
+            .outerRule(GrantPermissionRule.grant(Manifest.permission.READ_CALENDAR, Manifest.permission.WRITE_CALENDAR))
+            .around(InitCalendarProviderRule())
+
+    }
+
+    override fun before() {
+        if (!isInitialized) {
+            logger.info("Initializing calendar provider")
+            if (Build.VERSION.SDK_INT < 31)
+                logger.warning("Calendar provider initialization may or may not work. See InitCalendarProviderRule")
+
+            val context = InstrumentationRegistry.getInstrumentation().targetContext
+            val client = context.contentResolver.acquireContentProviderClient(CalendarContract.AUTHORITY)
+            Assert.assertNotNull("Couldn't acquire calendar provider", client)
+
+            client!!.use {
+                initCalendarProvider(client)
+                isInitialized = true
+            }
+        }
+    }
+
+    private fun initCalendarProvider(provider: ContentProviderClient) {
+        val account = Account("LocalCalendarTest", CalendarContract.ACCOUNT_TYPE_LOCAL)
+
+        // Sometimes, the calendar provider returns an ID for the created calendar, but then fails to find it.
+        var calendarOrNull: AndroidCalendar? = null
+        for (i in 0..50) {
+            calendarOrNull = createAndVerifyCalendar(account, provider)
+            if (calendarOrNull != null)
+                break
+            else
+                Thread.sleep(100)
+        }
+        val calendar = calendarOrNull ?: throw IllegalStateException("Couldn't create calendar")
+
+        try {
+            // single event init
+            val normalEvent = Event().apply {
+                dtStart = DtStart("20220120T010203Z")
+                summary = "Event with 1 instance"
+            }
+            val normalLocalEvent = AndroidEvent(calendar, normalEvent, null, null, null, 0)
+            normalLocalEvent.add()
+            AndroidEvent.Companion.numInstances(provider, account, normalLocalEvent.id!!)
+
+            // recurring event init
+            val recurringEvent = Event().apply {
+                dtStart = DtStart("20220120T010203Z")
+                summary = "Event over 22 years"
+                rRules.add(RRule("FREQ=YEARLY;UNTIL=20740119T010203Z"))     // year needs to be  >2074 (not supported by Android <11 Calendar Storage)
+            }
+            val localRecurringEvent = AndroidEvent(calendar, recurringEvent, null, null, null, 0)
+            localRecurringEvent.add()
+            AndroidEvent.Companion.numInstances(provider, account, localRecurringEvent.id!!)
+        } finally {
+            calendar.delete()
+        }
+    }
+
+    private fun createAndVerifyCalendar(account: Account, provider: ContentProviderClient): AndroidCalendar? {
+        val uri = AndroidCalendar.Companion.create(account, provider, ContentValues())
+
+        return try {
+            AndroidCalendar.Companion.findByID(
+                account,
+                provider,
+                AndroidCalendar.Factory,
+                ContentUris.parseId(uri)
+            )
+        } catch (e: Exception) {
+            logger.warning("Couldn't find calendar after creation: $e")
+            null
+        }
+    }
+
+}
\ No newline at end of file
diff --git a/lib/src/main/kotlin/at/bitfire/vcard4android/Contact.kt b/lib/src/main/kotlin/at/bitfire/vcard4android/Contact.kt
index 77573b98..3642f52d 100644
--- a/lib/src/main/kotlin/at/bitfire/vcard4android/Contact.kt
+++ b/lib/src/main/kotlin/at/bitfire/vcard4android/Contact.kt
@@ -13,11 +13,20 @@ import com.google.common.base.MoreObjects
 import ezvcard.VCardVersion
 import ezvcard.io.json.JCardReader
 import ezvcard.io.text.VCardReader
-import ezvcard.property.*
+import ezvcard.property.Address
+import ezvcard.property.Anniversary
+import ezvcard.property.Birthday
+import ezvcard.property.Email
+import ezvcard.property.Impp
+import ezvcard.property.Nickname
+import ezvcard.property.Organization
+import ezvcard.property.Related
+import ezvcard.property.Telephone
+import ezvcard.property.Url
 import java.io.IOException
 import java.io.OutputStream
 import java.io.Reader
-import java.util.*
+import java.util.LinkedList
 
 /**
  * Data class for a contact; between vCards and the Android contacts provider.
@@ -77,10 +86,6 @@ data class Contact(
 ) {
 
     companion object {
-        // productID (if set) will be used to generate a PRODID property.
-        // You may set this statically from the calling application.
-        var productID: String? = null
-
         const val DATE_PARAMETER_OMIT_YEAR = "X-APPLE-OMIT-YEAR"
         const val DATE_PARAMETER_OMIT_YEAR_DEFAULT = 1604
 
@@ -120,14 +125,14 @@ data class Contact(
 
 
     @Throws(IOException::class)
-    fun writeJCard(os: OutputStream) {
-        val generator = ContactWriter.fromContact(this, VCardVersion.V4_0)
+    fun writeJCard(os: OutputStream, productId: String) {
+        val generator = ContactWriter(this, VCardVersion.V4_0, productId)
         generator.writeCard(os, true)
     }
 
     @Throws(IOException::class)
-    fun writeVCard(vCardVersion: VCardVersion, os: OutputStream) {
-        val generator = ContactWriter.fromContact(this, vCardVersion)
+    fun writeVCard(vCardVersion: VCardVersion, os: OutputStream, productId: String) {
+        val generator = ContactWriter(this, vCardVersion, productId)
         generator.writeCard(os, false)
     }
 
diff --git a/lib/src/main/kotlin/at/bitfire/vcard4android/ContactWriter.kt b/lib/src/main/kotlin/at/bitfire/vcard4android/ContactWriter.kt
index 2cfc0450..826563f4 100644
--- a/lib/src/main/kotlin/at/bitfire/vcard4android/ContactWriter.kt
+++ b/lib/src/main/kotlin/at/bitfire/vcard4android/ContactWriter.kt
@@ -31,6 +31,7 @@ import ezvcard.property.DateOrTimeProperty
 import ezvcard.property.Kind
 import ezvcard.property.Member
 import ezvcard.property.Photo
+import ezvcard.property.ProductId
 import ezvcard.property.Related
 import ezvcard.property.Revision
 import ezvcard.property.StructuredName
@@ -47,15 +48,16 @@ import java.util.logging.Logger
  * to the vCard that is actually sent to the server.
  *
  * Properties which are not supported by the target vCard version have to be converted appropriately.
+ *
+ * @param contact       contact data to be converted into a vCard
+ * @param version       vCard version to generate
+ * @param productId     product ID that identifies your app (will be used as PRODID; ez-vcard version will be appended)
  */
-class ContactWriter private constructor(val contact: Contact, val version: VCardVersion) {
-
-    companion object {
-
-        fun fromContact(contact: Contact, version: VCardVersion) =
-            ContactWriter(contact, version)
-
-    }
+class ContactWriter(
+    val contact: Contact,
+    val version: VCardVersion,
+    val productId: String
+) {
 
     private val unknownProperties = LinkedList<VCardProperty>()
     val vCard = VCard()
@@ -73,8 +75,8 @@ class ContactWriter private constructor(val contact: Contact, val version: VCard
     }
 
     private fun addProperties() {
+        vCard.productId = ProductId("$productId (ez-vcard/${Ezvcard.VERSION})")
         contact.uid?.let { vCard.uid = Uid(it) }
-        Contact.productID?.let { vCard.setProductId(it) }
 
         addKindAndMembers()
         addFormattedName()
@@ -355,7 +357,7 @@ class ContactWriter private constructor(val contact: Contact, val version: VCard
         val writer =
             if (jCard)
                 JCardWriter(stream).apply {
-                    isAddProdId = Contact.productID == null
+                    isAddProdId = false     // we handle PRODID ourselves
                     registerCustomScribes()
 
                     // allow properties that are not defined in this vCard version
@@ -363,7 +365,7 @@ class ContactWriter private constructor(val contact: Contact, val version: VCard
                 }
             else
                 VCardWriter(stream, version).apply {
-                    isAddProdId = Contact.productID == null
+                    isAddProdId = false     // we handle PRODID ourselves
                     registerCustomScribes()
 
                     /* include trailing semicolons for maximum compatibility
diff --git a/lib/src/test/kotlin/at/bitfire/vcard4android/Constants.kt b/lib/src/test/kotlin/at/bitfire/vcard4android/Constants.kt
new file mode 100644
index 00000000..d5c9f939
--- /dev/null
+++ b/lib/src/test/kotlin/at/bitfire/vcard4android/Constants.kt
@@ -0,0 +1,9 @@
+/*
+ * This file is part of bitfireAT/synctools which is released under GPLv3.
+ * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package at.bitfire.vcard4android
+
+val testProductId = "bitfireAT/synctools test"
\ No newline at end of file
diff --git a/lib/src/test/kotlin/at/bitfire/vcard4android/ContactTest.kt b/lib/src/test/kotlin/at/bitfire/vcard4android/ContactTest.kt
index eb575700..71fd92cc 100644
--- a/lib/src/test/kotlin/at/bitfire/vcard4android/ContactTest.kt
+++ b/lib/src/test/kotlin/at/bitfire/vcard4android/ContactTest.kt
@@ -40,7 +40,7 @@ class ContactTest {
 
     private fun regenerate(c: Contact, vCardVersion: VCardVersion): Contact {
         val os = ByteArrayOutputStream()
-        c.writeVCard(vCardVersion, os)
+        c.writeVCard(vCardVersion, os, testProductId)
         return Contact.fromReader(InputStreamReader(ByteArrayInputStream(os.toByteArray()), Charsets.UTF_8), false,null).first()
     }
 
@@ -85,7 +85,7 @@ class ContactTest {
 
         // TEL
         assertEquals(2, c.phoneNumbers.size)
-        var phone = c.phoneNumbers.first
+        var phone = c.phoneNumbers.first()
         assertEquals("Useless", phone.label)
         assertTrue(phone.property.types.contains(TelephoneType.VOICE))
         assertTrue(phone.property.types.contains(TelephoneType.HOME))
@@ -99,7 +99,7 @@ class ContactTest {
 
         // EMAIL
         assertEquals(2, c.emails.size)
-        var email = c.emails.first
+        var email = c.emails.first()
         assertNull(email.label)
         assertTrue(email.property.types.contains(EmailType.HOME))
         assertTrue(email.property.types.contains(EmailType.PREF))
@@ -120,7 +120,7 @@ class ContactTest {
 
         // IMPP
         assertEquals(3, c.impps.size)
-        var impp = c.impps.first
+        var impp = c.impps.first()
         assertEquals("MyIM", impp.label)
         assertTrue(impp.property.types.contains(ImppType.PERSONAL))
         assertTrue(impp.property.types.contains(ImppType.MOBILE))
@@ -146,7 +146,7 @@ class ContactTest {
 
         // ADR
         assertEquals(2, c.addresses.size)
-        var addr = c.addresses.first
+        var addr = c.addresses.first()
         assertNull(addr.label)
         assertTrue(addr.property.types.contains(AddressType.WORK))
         assertTrue(addr.property.types.contains(AddressType.POSTAL))
@@ -203,14 +203,14 @@ class ContactTest {
         assertEquals(LocalDate.of(2014, 8, 12), c.anniversary!!.date)
         // X-ABDATE
         assertEquals(1, c.customDates.size)
-        c.customDates.first.also { date ->
+        c.customDates.first().also { date ->
             assertEquals("Custom Date", date.label)
             assertEquals(LocalDate.of(2021, 7, 29), date.property.date)
         }
 
         // RELATED
         assertEquals(2, c.relations.size)
-        var rel = c.relations.first
+        var rel = c.relations.first()
         assertTrue(rel.types.contains(RelatedType.CO_WORKER))
         assertTrue(rel.types.contains(RelatedType.CRUSH))
         assertEquals("Ägidius", rel.text)
@@ -229,19 +229,19 @@ class ContactTest {
         val c = regenerate(parseContact("allfields-vcard3.vcf"), VCardVersion.V4_0)
         // let's check only things that should be different when VCard 4.0 is generated
 
-        val phone = c.phoneNumbers.first.property
+        val phone = c.phoneNumbers.first().property
         assertFalse(phone.types.contains(TelephoneType.PREF))
         assertNotNull(phone.pref)
 
-        val email = c.emails.first.property
+        val email = c.emails.first().property
         assertFalse(email.types.contains(EmailType.PREF))
         assertNotNull(email.pref)
 
-        val impp = c.impps.first.property
+        val impp = c.impps.first().property
         assertFalse(impp.types.contains(ImppType.PREF))
         assertNotNull(impp.pref)
 
-        val addr = c.addresses.first.property
+        val addr = c.addresses.first().property
         assertFalse(addr.types.contains(AddressType.PREF))
         assertNotNull(addr.pref)
     }
diff --git a/lib/src/test/kotlin/at/bitfire/vcard4android/ContactWriterTest.kt b/lib/src/test/kotlin/at/bitfire/vcard4android/ContactWriterTest.kt
index 5b817f0b..301e1883 100644
--- a/lib/src/test/kotlin/at/bitfire/vcard4android/ContactWriterTest.kt
+++ b/lib/src/test/kotlin/at/bitfire/vcard4android/ContactWriterTest.kt
@@ -6,24 +6,44 @@
 
 package at.bitfire.vcard4android
 
-import at.bitfire.vcard4android.property.*
+import at.bitfire.vcard4android.property.CustomType
+import at.bitfire.vcard4android.property.XAbDate
+import at.bitfire.vcard4android.property.XAbLabel
+import at.bitfire.vcard4android.property.XAbRelatedNames
+import at.bitfire.vcard4android.property.XAddressBookServerKind
+import at.bitfire.vcard4android.property.XAddressBookServerMember
+import at.bitfire.vcard4android.property.XPhoneticFirstName
+import at.bitfire.vcard4android.property.XPhoneticLastName
+import at.bitfire.vcard4android.property.XPhoneticMiddleName
+import ezvcard.Ezvcard
 import ezvcard.VCard
 import ezvcard.VCardVersion
 import ezvcard.parameter.ImageType
 import ezvcard.parameter.RelatedType
-import ezvcard.property.*
+import ezvcard.property.Address
+import ezvcard.property.Anniversary
+import ezvcard.property.Birthday
+import ezvcard.property.Email
+import ezvcard.property.Impp
+import ezvcard.property.Kind
+import ezvcard.property.Nickname
+import ezvcard.property.Organization
+import ezvcard.property.Photo
+import ezvcard.property.Related
+import ezvcard.property.Revision
+import ezvcard.property.StructuredName
+import ezvcard.property.Telephone
+import ezvcard.property.Url
 import ezvcard.util.PartialDate
-import org.junit.Assert.*
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 import java.io.ByteArrayOutputStream
 import java.net.URI
-import java.time.Instant
 import java.time.LocalDate
-import java.time.LocalDateTime
-import java.time.ZoneId
 import java.time.ZoneOffset
 import java.time.ZonedDateTime
-import java.util.*
 
 class ContactWriterTest {
 
@@ -451,7 +471,7 @@ class ContactWriterTest {
                 values.add("nick1")
             })
         }
-        assertEquals(3 /* NICK + REV + FN */, vCard.properties.size)
+        assertEquals(4 /* PRODID + NICK + REV + FN */, vCard.properties.size)
         assertEquals("nick1", vCard.nickname.values.first())
     }
 
@@ -462,7 +482,7 @@ class ContactWriterTest {
                 values.add("nick1")
             }, "label1")
         }
-        assertEquals(4 /* NICK + X-ABLABEL + FN + REV */, vCard.properties.size)
+        assertEquals(5 /* PRODID + NICK + X-ABLABEL + FN + REV */, vCard.properties.size)
         vCard.nickname.apply {
             assertEquals("nick1", values.first())
             assertEquals("item1", group)
@@ -483,7 +503,7 @@ class ContactWriterTest {
                 values.add("nick1")
             }, "label1")
         }
-        assertEquals(5 /* X-TEST + NICK + X-ABLABEL + FN + REV */, vCard.properties.size)
+        assertEquals(6 /* PRODID + X-TEST + NICK + X-ABLABEL + FN + REV */, vCard.properties.size)
         vCard.nickname.apply {
             assertEquals("nick1", values.first())
             assertEquals("item2", group)
@@ -497,7 +517,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard3_Date() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V3_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V3_0, testProductId)
         val date = Birthday(LocalDate.of(121, 6, 30))
         generator.rewritePartialDate(date)
         assertEquals(LocalDate.of(121, 6, 30), date.date)
@@ -506,7 +526,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard4_Date() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V4_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V4_0, testProductId)
         val date = Birthday(LocalDate.of(121, 6, 30))
         generator.rewritePartialDate(date)
         assertEquals(LocalDate.of(121, 6, 30), date.date)
@@ -516,7 +536,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard3_PartialDateWithYear() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V3_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V3_0, testProductId)
         val date = Birthday(PartialDate.parse("20210730"))
         generator.rewritePartialDate(date)
         assertEquals(LocalDate.of(2021, 7, 30), date.date)
@@ -526,7 +546,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard4_PartialDateWithYear() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V4_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V4_0, testProductId)
         val date = Birthday(PartialDate.parse("20210730"))
         generator.rewritePartialDate(date)
         assertNull(date.date)
@@ -536,7 +556,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard3_PartialDateWithoutYear() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V3_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V3_0, testProductId)
         val date = Birthday(PartialDate.parse("--0730"))
         generator.rewritePartialDate(date)
         assertEquals(LocalDate.of(1604, 7, 30), date.date)
@@ -547,7 +567,7 @@ class ContactWriterTest {
 
     @Test
     fun testRewritePartialDate_vCard4_PartialDateWithoutYear() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V4_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V4_0, testProductId)
         val date = Birthday(PartialDate.parse("--0730"))
         generator.rewritePartialDate(date)
         assertNull(date.date)
@@ -558,27 +578,30 @@ class ContactWriterTest {
 
     @Test
     fun testWriteJCard() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V4_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V4_0, testProductId)
         generator.vCard.revision = Revision(
             ZonedDateTime.of(2021, 7, 30, 1, 2, 3, 0, ZoneOffset.UTC)
         )
 
         val stream = ByteArrayOutputStream()
         generator.writeCard(stream, true)
-        assertEquals("[\"vcard\",[[\"version\",{},\"text\",\"4.0\"],[\"prodid\",{},\"text\",\"ez-vcard 0.12.1\"],[\"fn\",{},\"text\",\"\"],[\"rev\",{},\"timestamp\",\"2021-07-30T01:02:03+00:00\"]]]", stream.toString())
+        assertEquals(
+            "[\"vcard\",[[\"version\",{},\"text\",\"4.0\"],[\"prodid\",{},\"text\",\"$testProductId (ez-vcard/${Ezvcard.VERSION})\"],[\"fn\",{},\"text\",\"\"],[\"rev\",{},\"timestamp\",\"2021-07-30T01:02:03+00:00\"]]]",
+            stream.toString()
+        )
     }
 
 
     @Test
     fun testWriteVCard() {
-        val generator = ContactWriter.fromContact(Contact(), VCardVersion.V4_0)
+        val generator = ContactWriter(Contact(), VCardVersion.V4_0, testProductId)
         generator.vCard.revision = Revision(ZonedDateTime.of(2021, 7, 30, 1, 2, 3, 0, ZoneOffset.UTC))
 
         val stream = ByteArrayOutputStream()
         generator.writeCard(stream, false)
         assertEquals("BEGIN:VCARD\r\n" +
                 "VERSION:4.0\r\n" +
-                "PRODID:ez-vcard 0.12.1\r\n" +
+                "PRODID:$testProductId (ez-vcard/${Ezvcard.VERSION})\r\n" +
                 "FN:\r\n" +
                 "REV:20210730T010203+0000\r\n" +
                 "END:VCARD\r\n", stream.toString())
@@ -594,9 +617,8 @@ class ContactWriterTest {
                 country = "Line2"
             })
         }
-        ContactWriter
-                .fromContact(contact, VCardVersion.V4_0)
-                .writeCard(stream, false)
+        ContactWriter(contact, VCardVersion.V4_0, testProductId)
+            .writeCard(stream, false)
         assertTrue(stream.toString().contains("ADR;LABEL=\"Li^^ne 1,1 - ^' -\":;;Line1;;;;Line2"))
     }
 
@@ -606,7 +628,7 @@ class ContactWriterTest {
     private fun generate(version: VCardVersion = VCardVersion.V4_0, prepare: Contact.() -> Unit): VCard {
         val contact = Contact()
         contact.run(prepare)
-        return ContactWriter.fromContact(contact, version).vCard
+        return ContactWriter(contact, version, testProductId).vCard
     }
 
 }
\ No newline at end of file
diff --git a/settings.gradle.kts b/settings.gradle.kts
index a0e20df4..bbf8ff3a 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -1,3 +1,9 @@
+/*
+ * This file is part of bitfireAT/synctools which is released under GPLv3.
+ * Copyright © All Contributors. See the LICENSE and AUTHOR files in the root directory for details.
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
 pluginManagement {
     repositories {
         google()
@@ -14,6 +20,5 @@ dependencyResolutionManagement {
     }
 }
 
-rootProject.name = "root"
-include(":lib")
-project(":lib").name = "synctools"
\ No newline at end of file
+rootProject.name = "synctools"
+include(":lib")
\ No newline at end of file