Mobile Testing

What it is

Mobile testing verifies apps that run on devices you do not control: different OS versions, screen sizes, network conditions and hardware. It splits into two families that cover different kinds of behaviour.

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unit / widget  → fast, on-host: logic, view models, composables
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UI / E2E       → a real device or emulator exercising the full app

UI tests further split by reach: a white-box test (Espresso, XCUITest) runs inside the app process and can see internals, while a black-box test (Appium, Maestro) drives the app the way a user does. Real-device clouds (Firebase Test Lab, BrowserStack App Automate) fill the gaps in your local device matrix.

When to use it / when to avoid it

Use it for

Critical journeys on each platform: onboarding, login, checkout, permissions
Platform-specific behaviour: notifications, deep links, biometrics, rotation
Verifying release builds on a representative device and OS matrix
Flows that depend on device capabilities (camera, GPS, offline mode)

Avoid it when

The behaviour is pure logic that a faster unit or widget test can cover
You are testing the same journey exhaustively on every device — sample the matrix instead
A shared cross-platform flow is already covered on one platform and the code is common
You need web-only checks — that is cross-browser

Frameworks & tools

Tool	Ecosystem	Notes
Appium	Multi (Android, iOS, web)	WebDriver protocol, cross-platform, black-box
Espresso	Android (Kotlin/Java)	Fast white-box UI tests in-process
XCUITest	iOS (Swift/Obj-C)	Apple’s native UI testing framework
Detox	React Native	Gray-box, auto-synchronises with the app
Maestro	Multi (Android, iOS, web)	YAML flows, low-flake, easy onboarding
Firebase Test Lab	Android, iOS	Real and virtual devices in the cloud
BrowserStack App Automate	Multi	Real device cloud for Appium/Espresso/XCUITest

Quick setup

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npm install -g appium
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appium driver install uiautomator2
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appium driver install xcuitest
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appium

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npm install -D detox
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npx detox build --configuration ios.sim.debug
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npx detox test --configuration ios.sim.debug

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androidTestImplementation("androidx.test.espresso:espresso-core:3.6.1")
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androidTestImplementation("androidx.test.ext:junit:1.2.1")

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// Add a UI Testing Bundle target in Xcode,
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// then run with: xcodebuild test -scheme MyApp -destination 'platform=iOS Simulator,name=iPhone 15'

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flutter test integration_test/app_test.dart

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pip install Appium-Python-Client

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<dependency>
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  <groupId>io.appium</groupId>
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  <artifactId>java-client</artifactId>
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  <version>9.3.0</version>
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  <scope>test</scope>
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</dependency>

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dotnet add package Appium.WebDriver

Example

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it('logs in on Android', async () => {
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  await $('~email').setValue('ada@example.com');
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  await $('~password').setValue('s3cret');
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  await $('~login').click();
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  await expect($('~dashboard')).toBeDisplayed();
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});

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def test_dang_nhap(driver):
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    driver.find_element(AppiumBy.ACCESSIBILITY_ID, "email").send_keys("ada@example.com")
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    driver.find_element(AppiumBy.ACCESSIBILITY_ID, "password").send_keys("s3cret")
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    driver.find_element(AppiumBy.ACCESSIBILITY_ID, "login").click()
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    assert driver.find_element(AppiumBy.ACCESSIBILITY_ID, "dashboard").is_displayed()

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@Test
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fun loginReachesDashboard() {
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    onView(withId(R.id.email)).perform(typeText("ada@example.com"))
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    onView(withId(R.id.password)).perform(typeText("s3cret"), closeSoftKeyboard())
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    onView(withId(R.id.login)).perform(click())
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    onView(withId(R.id.dashboard)).check(matches(isDisplayed()))
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}

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func testLoginReachesDashboard() {
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    let app = XCUIApplication()
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    app.launch()
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    app.textFields["email"].tap()
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    app.textFields["email"].typeText("ada@example.com")
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    app.secureTextFields["password"].tap()
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    app.secureTextFields["password"].typeText("s3cret")
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    app.buttons["login"].tap()
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    XCTAssertTrue(app.otherElements["dashboard"].waitForExistence(timeout: 5))
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}

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appId: com.example.app
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---
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- launchApp
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- tapOn: "email"
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- inputText: "ada@example.com"
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- tapOn: "password"
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- inputText: "s3cret"
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- tapOn: "login"
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- assertVisible: "dashboard"

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func TestLogin(t *testing.T) {
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  session := mustCreateSession(t) // POST /session
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  defer deleteSession(t, session)
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 findByID(t, session, "email").SendKeys("ada@example.com")
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 findByID(t, session, "password").SendKeys("s3cret")
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 findByID(t, session, "login").Click()
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 assertDisplayed(t, findByID(t, session, "dashboard"))
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}

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@Test
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void loginReachesDashboard() {
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  driver.findElement(AppiumBy.accessibilityId("email")).sendKeys("ada@example.com");
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  driver.findElement(AppiumBy.accessibilityId("password")).sendKeys("s3cret");
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  driver.findElement(AppiumBy.accessibilityId("login")).click();
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  assertTrue(driver.findElement(AppiumBy.accessibilityId("dashboard")).isDisplayed());
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}

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[Fact]
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public void LoginReachesDashboard()
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{
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    _driver.FindElement(MobileBy.AccessibilityId("email")).SendKeys("ada@example.com");
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    _driver.FindElement(MobileBy.AccessibilityId("password")).SendKeys("s3cret");
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    _driver.FindElement(MobileBy.AccessibilityId("login")).Click();
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    Assert.True(_driver.FindElement(MobileBy.AccessibilityId("dashboard")).Displayed);
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}

Anti-patterns & best practices

Prefer accessibility IDs. Coordinates and screen positions break on the next device.
Wait for state, not the clock. Use framework synchronization and explicit waits over fixed sleeps.
Sample the device matrix. Cover OS extremes, one low-end device and one large screen, not every model.
Reset app state per test. Fresh install or deep clean avoids order-dependent flakiness.
Run the slow device suite on a cloud and keep fast unit and widget tests local.
Test the release build too. Debug-only behaviour and ProGuard/R8 stripping can break shipped apps.