得到

Jetpack-Compose-Playground/docs/general/testing.md

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+# UI Testing
+
+## Setup
+Add the Compose testing library to your dependencies in build.gradle
+
+```kotlin
+androidTestImplementation("androidx.compose.ui:ui-test:$compose_version")
+debugImplementation("androidx.compose.ui:ui-test-manifest:$compose_version")
+```
+
+## Example
+Let's say you have the following example code, it's a button with a text that says **Hello** and when you click on it, it turns to **Bye**
+
+```kotlin
+@Composable
+fun TestingExample() {
+    val state = remember { mutableStateOf("Hello") }
+    Button(onClick = { state.value = "Bye" }) {
+        Text(state.value)
+    }
+}
+```
+
+
+## TestRule
+To run this Composable in your test Code you have 2 options:
+
+### 1) createComposeRule()
+```kotlin
+@Rule
+@JvmField
+var composeTestRule: ComposeContentTestRule = createComposeRule()
+```
+
+You can use this when you want to run your Composable without a specific Activity. You can then use the **setContent()** from the TestRule to host your Composable.
+
+```kotlin
+composeTestRule.setContent {
+    TestingExample()
+}
+```
+
+
+### 2) createAndroidComposeRule()
+```kotlin
+@Rule
+@JvmField
+var composeTestRule: ComposeContentTestRule = createAndroidComposeRule<UiTestingDemoActivity>()
+```
+
+You can use this when you want to start your test with a specific Activity.
+
+## Interaction with Composables
+
+Now we want to test how the Composable reacts when we interact with it. 
+Usually in Tests we would use Espresso for that, but you can use that only for classic Android Views and not for Composables.
+
+The ComposeTestRule will offer a similar API
+
+```kotlin
+class ExampleUiTestWithAndroidComposeRule {
+
+    @Rule
+    @JvmField
+    var composeTestRule: ComposeContentTestRule = createAndroidComposeRule<UiTestingDemoActivity>()
+
+    @Test
+    fun whenIClickOnButton_TheTextShouldChange() {
+        composeTestRule.onNodeWithText("Hello").assertExists()
+        composeTestRule.onNodeWithText("Hello").performClick()
+        composeTestRule.onNodeWithText("Hello").assertDoesNotExist()
+        composeTestRule.onNodeWithText("Bye").assertExists()
+    }
+
+}
+```
+
+As you can see above we used the TestRule methods to click on the node with the text **Hello** and asserted that the text changed to **Bye**
+
+The TestRule offers a lot of different methods. You can find a cheatSheet [here](https://developer.android.com/jetpack/compose/testing-cheatsheet) 
+
+### TestTags
+The test above is only half correct, because it looks for the text inside the button and not the button itself.
+Composables have no resource ids so we cant just use **onView(withId(R.id.my_view))** to find a Composable in a test, also we can't find Composables of a specific "type" 
+like a button, because everything is just a Composable function. 
+
+When you can't find a Composable by a text and you want to make it detectable in your test. Jetpack Compose offers the concept of a **TestTag**.
+testTag is a modifier that needs to be set to a Composable. It expects a string which will be used as a reference in your test.
+
+```kotlin
+@Composable
+fun TestingExample() {
+    val state = remember { mutableStateOf("Hello") }
+    Button(onClick = { state.value = "Bye" }, modifier = Modifier.testTag("MyTestTag")) {
+        Text(state.value)
+    }
+}
+```
+
+Now you can use **onNodeWithTag("MyTestTag")** to find the button Composable.
+
+```kotlin
+@Test
+fun whenIClickOnButton_TheTextShouldChange() {
+    composeTestRule.onNodeWithTag("MyTestTag").assertTextEquals("Hello")
+    composeTestRule.onNodeWithTag("MyTestTag").performClick()
+    composeTestRule.onNodeWithText("Hello").assertDoesNotExist()
+    composeTestRule.onNodeWithTag("MyTestTag").assertTextEquals("Bye")
+}
+```
+
+### PrintToLog
+When you want to get more information about how the node tree of a Composable looks like, 
+you can use **printToLog()** on a node.
+
+```kotlin
+composeTestRule.onNodeWithTag("MyTestTag").printToLog("XXX")
+```
+
+will print to logcat:
+
+```kotlin
+2022-01-07 22:58:55.048 9567-9587/de.jensklingenberg.jetpackcomposeplayground D/XXX: printToLog:
+Printing with useUnmergedTree = 'false'
+Node #2 at (l=0.0, t=325.0, r=195.0, b=424.0)px, Tag: 'MyTestTag'
+Role = 'Button'
+Text = '[Hello]'
+Actions = [OnClick, GetTextLayoutResult]
+MergeDescendants = 'true'
+```
+
+## See also:
+* [Full Example Code](https://github.com/Foso/Jetpack-Compose-Playground/blob/master/app/src/androidTest/java/de/jensklingenberg/jetpackcomposeplayground/ExampleUiTestWithAndroidComposeRule.kt)
+* [Full Example Code](https://github.com/Foso/Jetpack-Compose-Playground/blob/master/app/src/androidTest/java/de/jensklingenberg/jetpackcomposeplayground/ExampleUiTestWithComposeRule.kt)