Repo created

core/testing/build.gradle.kts

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+plugins {
+    id(ThunderbirdPlugins.Library.jvm)
+}
+
+dependencies {
+    implementation(libs.assertk)
+}

core/testing/src/main/kotlin/app/k9mail/core/testing/TestClock.kt

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+package app.k9mail.core.testing
+
+import kotlin.time.Duration
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+class TestClock(
+    private var currentTime: Instant = Clock.System.now(),
+) : Clock {
+    override fun now(): Instant = currentTime
+
+    fun changeTimeTo(time: Instant) {
+        currentTime = time
+    }
+
+    fun advanceTimeBy(duration: Duration) {
+        currentTime += duration
+    }
+}

core/testing/src/main/kotlin/assertk/assertions/ListExtensions.kt

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+package assertk.assertions
+
+import assertk.Assert
+import assertk.assertions.support.expected
+import assertk.assertions.support.show
+
+fun <T> Assert<List<T>>.containsNoDuplicates() = given { actual ->
+    val seen: MutableSet<T> = mutableSetOf()
+    val duplicates = actual.filter { !seen.add(it) }
+    if (duplicates.isNotEmpty()) {
+        expected("to contain no duplicates but found: ${show(duplicates)}")
+    }
+}

core/testing/src/test/kotlin/app/k9mail/core/testing/TestClockTest.kt

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+package app.k9mail.core.testing
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import kotlin.test.Test
+import kotlin.time.Duration.Companion.milliseconds
+import kotlinx.datetime.Instant
+
+internal class TestClockTest {
+
+    @Test
+    fun `should return the current time`() {
+        val testClock = TestClock(Instant.DISTANT_PAST)
+
+        val currentTime = testClock.now()
+
+        assertThat(currentTime).isEqualTo(Instant.DISTANT_PAST)
+    }
+
+    @Test
+    fun `should return the changed time`() {
+        val testClock = TestClock(Instant.DISTANT_PAST)
+        testClock.changeTimeTo(Instant.DISTANT_FUTURE)
+
+        val currentTime = testClock.now()
+
+        assertThat(currentTime).isEqualTo(Instant.DISTANT_FUTURE)
+    }
+
+    @Test
+    fun `should advance time by duration`() {
+        val testClock = TestClock(Instant.DISTANT_PAST)
+        testClock.advanceTimeBy(1L.milliseconds)
+
+        val currentTime = testClock.now()
+
+        assertThat(currentTime).isEqualTo(Instant.DISTANT_PAST + 1L.milliseconds)
+    }
+}

core/testing/src/test/kotlin/assertk/assertions/ListExtensionsKtTest.kt

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+package assertk.assertions
+
+import assertk.assertThat
+import kotlin.test.Test
+
+class ListExtensionsKtTest {
+
+    @Test
+    fun `containsNoDuplicates() should succeed with no duplicates`() {
+        val list = listOf("a", "b", "c")
+
+        assertThat(list).containsNoDuplicates()
+    }
+
+    @Test
+    fun `containsNoDuplicates() should fail with duplicates`() {
+        val list = listOf("a", "b", "c", "a", "a")
+
+        assertThat {
+            assertThat(list).containsNoDuplicates()
+        }.isFailure()
+            .hasMessage(
+                """
+                expected to contain no duplicates but found: <["a", "a"]>
+                """.trimIndent(),
+            )
+    }
+}