KTLN-547: Unit tests for Sorting String dates (#848)

* KTLN-547: Unit tests for Sorting String dates

Signed-off-by: Diego Torres <[email protected]>

* KTLN-547: Fixed class name

Signed-off-by: Diego Torres <[email protected]>

* KTLN-547: Improvements in unit tests

Signed-off-by: Diego Torres <[email protected]>

---------

Signed-off-by: Diego Torres <[email protected]>

Author: diegotorrespy

core-kotlin-modules/core-kotlin-collections-6/src/test/kotlin/com/baeldung/listofdates/SortingListOfStringDatesUnitTest.kt

@@ -0,0 +1,53 @@
+package com.baeldung.listofdates
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import java.text.SimpleDateFormat
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+import kotlin.test.assertNotNull
+
+class SortingListOfStringDatesUnitTest {
+
+    @Test
+    fun `given a list of string dates when sorting with DateTimeFormatter then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val dateFormat = SimpleDateFormat("dd-MM-yyyy")
+
+        val sortedDates = dates.sortedByDescending { dateFormat.parse(it) }
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+
+    @Test
+    fun `given a list of string dates when sorting with LocalDate then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val dateFormatter = DateTimeFormatter.ofPattern("dd-MM-yyyy")
+        val sortedDates = dates.sortedByDescending { LocalDate.parse(it, dateFormatter) }
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+
+    @Test
+    fun `given a list of string dates when sorting using custom comparator then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val sortedDates = dates.sortedWith(compareByDescending {
+            val (day, month, year) = it.split("-")
+            "$year-$month-$day"
+        })
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+}