add BackDispatcherTest

buildSrc/src/main/kotlin/Versions.kt

@@ -11,7 +11,7 @@ object Versions {
 
     object Kotlin {
         const val lang = "1.8.20"
-        const val coroutines = "1.6.4"
+        const val coroutines = "1.7.1"
     }
 
     object Java {

precompose/build.gradle.kts

@@ -49,6 +49,7 @@ kotlin {
                 api(compose.animation)
                 implementation(kotlin("test-common"))
                 implementation(kotlin("test-annotations-common"))
+                implementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:${Versions.Kotlin.coroutines}")
                 // @OptIn(org.jetbrains.compose.ExperimentalComposeLibrary::class)
                 // implementation(compose.uiTestJUnit4)
             }

precompose/src/commonMain/kotlin/moe/tlaster/precompose/ui/BackPressAdapter.kt

@@ -12,7 +12,8 @@ interface BackDispatcherOwner {
 }
 
 class BackDispatcher {
-    private val handlers = arrayListOf<BackHandler>()
+    // internal for testing
+    internal val handlers = arrayListOf<BackHandler>()
 
     fun onBackPress() {
         handlers.lastOrNull {

precompose/src/commonTest/kotlin/moe/tlaster/precompose/navigation/BackDispatcherTest.kt

@@ -0,0 +1,47 @@
+package moe.tlaster.precompose.navigation
+
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import moe.tlaster.precompose.ui.BackDispatcher
+import moe.tlaster.precompose.ui.BackHandler
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class BackDispatcherTest {
+
+    @Test
+    fun onBackPress_should_call_handleBackPress_on_the_last_enabled_handler() {
+        val dispatcher = BackDispatcher()
+        val handler1 = object : BackHandler {
+            override val isEnabled = true
+            override fun handleBackPress() {}
+        }
+        val handler2 = object : BackHandler {
+            override val isEnabled = true
+            override fun handleBackPress() {}
+        }
+        dispatcher.register(handler1)
+        dispatcher.register(handler2)
+
+        dispatcher.onBackPress()
+
+        assertEquals(handler2, dispatcher.handlers.last())
+    }
+
+    @Test
+    fun canHandleBackPress_should_return_true_if_any_handler_is_enabled() = runTest {
+        val dispatcher = BackDispatcher()
+        val handler1 = object : BackHandler {
+            override val isEnabled = true
+            override fun handleBackPress() {}
+        }
+        val handler2 = object : BackHandler {
+            override val isEnabled = true
+            override fun handleBackPress() {}
+        }
+        dispatcher.register(handler1)
+        dispatcher.register(handler2)
+
+        assertEquals(true, dispatcher.canHandleBackPress.first())
+    }
+}