UI testing tutorial (#3552)

See https://youtrack.jetbrains.com/issue/COMPOSE-314/Stabilize-ui-test-framework, p.4

tutorials/README.md

@@ -18,6 +18,7 @@
 * [Navigation](Navigation)
 * [Accessibility](Accessibility)
 * [Building a native distribution](Native_distributions_and_local_execution)
+* [UI testing](UI_Testing)
 
 ## Web
 * [Getting started](https://kotl.in/wasm-compose-example)

tutorials/UI_Testing/README.md

@@ -0,0 +1,78 @@
+# UI Testing
+The API for unit testing in Compose for Desktop is nearly identical to the [Jetpack Compose Android testing API](https://developer.android.com/jetpack/compose/testing). We highly recommended reading that first before moving on to this tutorial.
+
+## Setting up
+To start using the testing API, you will need to add the dependency on `compose.uiTestJUnit4` to your `build.gradle` file and create the directory for your tests. 
+
+If the module is desktop-only (`kotlin("jvm")` is applied), add the dependency via:
+```kotlin
+dependencies {
+    testImplementation(compose.desktop.uiTestJUnit4)
+    testImplementation(compose.desktop.currentOs)
+}
+```
+
+and the directory for tests will be `src/test/kotlin`
+
+If the module is multiplatform (`kotlin(“multiplatform”)` is applied), add it via:
+
+```kotlin
+kotlin {
+    sourceSets {
+        val desktopTest by getting {
+            dependencies {
+                implementation(compose.desktop.uiTestJUnit4)
+                implementation(compose.desktop.currentOs)
+            }
+        }
+    }
+}
+```
+
+And the directory for tests will be `src/desktopTest/kotlin`
+
+## Creating your first test
+In the tests directory, create a file named `ExampleTest.kt` and paste this code into it:
+
+```kotlin
+import androidx.compose.material.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.test.*
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.test.junit4.createComposeRule
+import org.junit.Rule
+import org.junit.Test
+
+class ExampleTest {
+    @get:Rule
+    val rule = createComposeRule()
+
+    @Test
+    fun myTest(){
+        rule.setContent {
+            var text by remember { mutableStateOf("Hello") }
+            Text(
+                text = text,
+                modifier = Modifier.testTag("text")
+            )
+            Button(
+                onClick = { text = "Compose" },
+                modifier = Modifier.testTag("button")
+            ){
+                Text("Click me")
+            }
+        }
+
+        rule.onNodeWithTag("text").assertTextEquals("Hello")
+        rule.onNodeWithTag("button").performClick()
+        rule.onNodeWithTag("text").assertTextEquals("Compose")
+    }
+}
+```
+
+Now you can run the test by either clicking ![run](https://github.com/JetBrains/compose-multiplatform/assets/5963351/2eac4041-757e-48b0-9dc2-baef82f21a7b) button in your IDE, or from the command line with
+```
+./gradlew test
+```
+