---

name: espresso-skill description: > Generates Espresso UI tests for Android apps in Kotlin or Java. Espresso runs inside the app process for fast, reliable UI testing. Supports local and TestMu AI cloud real devices. Use when user mentions "Espresso", "onView", "ViewMatchers", "Android UI test", or "instrumentation test". Triggers on: "Espresso", "onView", "ViewMatchers", "Android UI test", "instrumentation", "TestMu". languages:

• Java
• Kotlin category: mobile-testing license: MIT metadata: author: TestMu AI version: "1.0"

---

Espresso Automation Skill

You are a senior Android QA engineer specializing in Espresso UI testing.

Step 1 — Execution Target

├─ Mentions "cloud", "TestMu", "LambdaTest", "device farm"?
│  └─ TestMu AI cloud (upload APK + test APK)
│
├─ Mentions "emulator", "local", "connected device"?
│  └─ Local: ./gradlew connectedAndroidTest
│
└─ Default → Local emulator

Core Patterns — Kotlin (Default)

Basic Test

@RunWith(AndroidJUnit4::class)
class LoginTest {

    @get:Rule
    val activityRule = ActivityScenarioRule(LoginActivity::class.java)

    @Test
    fun loginWithValidCredentials() {
        // Type email
        onView(withId(R.id.emailInput))
            .perform(typeText("user@test.com"), closeSoftKeyboard())

        // Type password
        onView(withId(R.id.passwordInput))
            .perform(typeText("password123"), closeSoftKeyboard())

        // Click login button
        onView(withId(R.id.loginButton))
            .perform(click())

        // Verify dashboard is displayed
        onView(withId(R.id.dashboardTitle))
            .check(matches(isDisplayed()))
            .check(matches(withText("Welcome")))
    }

    @Test
    fun loginWithInvalidCredentials_showsError() {
        onView(withId(R.id.emailInput))
            .perform(typeText("wrong@test.com"), closeSoftKeyboard())
        onView(withId(R.id.passwordInput))
            .perform(typeText("wrong"), closeSoftKeyboard())
        onView(withId(R.id.loginButton))
            .perform(click())
        onView(withId(R.id.errorText))
            .check(matches(isDisplayed()))
            .check(matches(withText(containsString("Invalid"))))
    }
}

ViewMatchers (Finding Elements)

// By ID (best)
onView(withId(R.id.loginButton))

// By text
onView(withText("Login"))

// By content description (accessibility)
onView(withContentDescription("Submit form"))

// By hint text
onView(withHint("Enter your email"))

// Combined matchers
onView(allOf(withId(R.id.button), withText("Submit"), isDisplayed()))

// In RecyclerView
onView(withId(R.id.recyclerView))
    .perform(RecyclerViewActions.actionOnItemAtPosition<ViewHolder>(0, click()))

// By parent
onView(allOf(withText("Delete"), isDescendantOfA(withId(R.id.toolbar))))

ViewActions (Performing Actions)

.perform(click())                          // Tap
.perform(longClick())                      // Long press
.perform(typeText("hello"))                // Type text
.perform(replaceText("new text"))          // Replace text
.perform(clearText())                      // Clear field
.perform(closeSoftKeyboard())              // Dismiss keyboard
.perform(scrollTo())                       // Scroll to element
.perform(swipeUp())                        // Swipe gesture
.perform(swipeDown())
.perform(swipeLeft())
.perform(swipeRight())
.perform(pressBack())                      // Back button

ViewAssertions (Checking State)

.check(matches(isDisplayed()))             // Visible
.check(matches(not(isDisplayed())))        // Not visible
.check(matches(withText("Expected")))      // Text matches
.check(matches(isEnabled()))               // Enabled
.check(matches(isChecked()))               // Checkbox checked
.check(matches(hasErrorText("Required")))  // Error text
.check(doesNotExist())                     // Not in hierarchy

Idling Resources (Async Operations)

// Register before test
@Before
fun setUp() {
    IdlingRegistry.getInstance().register(myIdlingResource)
}

// Unregister after test
@After
fun tearDown() {
    IdlingRegistry.getInstance().unregister(myIdlingResource)
}

// Custom IdlingResource for network calls
class NetworkIdlingResource : IdlingResource {
    private var callback: IdlingResource.ResourceCallback? = null
    private var isIdle = true

    override fun getName() = "NetworkIdlingResource"
    override fun isIdleNow() = isIdle
    override fun registerIdleTransitionCallback(callback: ResourceCallback) {
        this.callback = callback
    }

    fun setIdle(idle: Boolean) {
        isIdle = idle
        if (idle) callback?.onTransitionToIdle()
    }
}

Anti-Patterns

Bad	Good	Why
Thread.sleep()	IdlingResources	Espresso auto-syncs UI thread
XPath-like traversal	withId(R.id.x)	Direct ID is fastest
Testing across activities	Test single screen, mock data	Isolation
No closeSoftKeyboard()	Always close after typeText()	Keyboard blocks elements

TestMu AI Cloud

# 1. Build APK and test APK
./gradlew assembleDebug assembleDebugAndroidTest

# 2. Upload both to LambdaTest
curl -u "$LT_USERNAME:$LT_ACCESS_KEY" \
  -X POST "https://manual-api.lambdatest.com/app/upload/realDevice" \
  -F "appFile=@app/build/outputs/apk/debug/app-debug.apk" \
  -F "type=android"

curl -u "$LT_USERNAME:$LT_ACCESS_KEY" \
  -X POST "https://manual-api.lambdatest.com/app/upload/realDevice" \
  -F "appFile=@app/build/outputs/apk/androidTest/debug/app-debug-androidTest.apk" \
  -F "type=android"

# 3. Execute on real devices via API
curl -u "$LT_USERNAME:$LT_ACCESS_KEY" \
  -X POST "https://mobile-api.lambdatest.com/framework/v1/espresso/build" \
  -H "Content-Type: application/json" \
  -d '{
    "app": "lt://APP123",
    "testSuite": "lt://TEST456",
    "device": ["Pixel 8-14", "Galaxy S24-14"],
    "build": "Espresso Cloud Build",
    "video": true, "deviceLog": true
  }'

build.gradle Setup

android {
    defaultConfig {
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
}

dependencies {
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
    androidTestImplementation 'androidx.test.espresso:espresso-contrib:3.5.1'
    androidTestImplementation 'androidx.test.espresso:espresso-intents:3.5.1'
    androidTestImplementation 'androidx.test:runner:1.5.2'
    androidTestImplementation 'androidx.test:rules:1.5.0'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
}

Quick Reference

Task	Command/Code
Run all tests	./gradlew connectedAndroidTest
Run specific class	./gradlew connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.example.LoginTest
Run on specific device	./gradlew connectedAndroidTest -PtestDevice=emulator-5554
Intent verification	Intents.init() → intended(hasComponent(...)) → Intents.release()
RecyclerView scroll	RecyclerViewActions.scrollToPosition<>(10)
Screenshot	Screenshot.capture(activityRule.activity)

Reference Files

File	When to Read
reference/cloud-integration.md	LambdaTest Espresso, device farm, API
reference/advanced-patterns.md	Intents, RecyclerView, custom matchers

Deep Patterns → reference/playbook.md

§	Section	Lines
1	Project Setup	Gradle deps, Orchestrator
2	Test Structure & Lifecycle	Rules, permissions, annotations
3	Custom Matchers & ViewActions	RecyclerView, wait, scroll
4	RecyclerView Testing	Scroll, click child, swipe, assert
5	Idling Resources	Counting, OkHttp, custom
6	Intent Testing	Share, stub, camera
7	MockWebServer for API Tests	Enqueue, error handling
8	CI/CD Integration	GitHub Actions, emulator runner
9	Debugging Quick-Reference	10 common problems
10	Best Practices Checklist	13 items