Add ListTasks usecase

Author: Gerrit Garbereder

Task-Tracker-Usecases/src/commonMain/kotlin/com/garbereder/tasktracker/usecases/tasks/ListTasks.kt

@@ -0,0 +1,9 @@
+package com.garbereder.tasktracker.usecases.tasks
+
+import com.garbereder.tasktracker.entities.Task
+import com.garbereder.tasktracker.entities.TaskCollection
+import com.garbereder.tasktracker.usecases.UseCase
+
+class ListTasks(private val collection: TaskCollection): UseCase<Iterator<Task>> {
+    override fun invoke(): Iterator<Task> = collection.iterator()
+}

Task-Tracker-Usecases/src/commonTest/kotlin/com/garbereder/tasktracker/usecases/tasks/ListTasksTests.kt

@@ -0,0 +1,34 @@
+package com.garbereder.tasktracker.usecases.tasks
+
+import com.garbereder.tasktracker.entities.Task
+import com.garbereder.tasktracker.entities.TaskCollection
+import io.mockative.*
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class ListTasksTests {
+    @Mock
+    val collection = mock(classOf<TaskCollection>())
+
+    @Test
+    fun invoke_noInput_callsThrough() {
+        val tasks = listOf(
+            Task("1","TaskName"),
+            Task("1","TaskName2")
+        )
+        given(collection).invocation { iterator() }
+            .then { tasks.iterator() }
+
+        val it = ListTasks(collection).invoke()
+
+        verify(collection).invocation { iterator() }
+            .wasInvoked(exactly = once)
+
+        assertTrue ( it.hasNext() )
+        assertEquals(tasks[0], it.next())
+        assertEquals(tasks[1], it.next())
+        assertFalse ( it.hasNext() )
+    }
+}