Make a screenshot when test fails to help with debugging

.gitlab-ci.yml

@@ -35,12 +35,15 @@ android test:
     - start-emulator.sh
     # run normal and screenshot tests together (exclude Large tests)
     - ./gradlew -Djava.security.egd=file:/dev/urandom connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.notAnnotation=androidx.test.filters.LargeTest
+  after_script:
+    - adb pull /sdcard/Pictures/screenshots
   artifacts:
     name: "${CI_PROJECT_PATH}_${CI_JOB_STAGE}_${CI_COMMIT_REF_NAME}_${CI_COMMIT_SHA}"
     paths:
       - kernel.log
       - logcat.txt
       - briar-android/build/reports/androidTests/connected/flavors/*
+      - screenshots
     expire_in: 3 days
     when: on_failure
   when: manual

briar-android/src/androidTest/java/org/briarproject/briar/android/ScreenshotOnFailureRule.java

@@ -0,0 +1,65 @@
+package org.briarproject.briar.android;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import java.io.IOException;
+import java.util.HashSet;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import androidx.test.espresso.Espresso;
+import androidx.test.espresso.FailureHandler;
+import androidx.test.espresso.base.DefaultFailureHandler;
+import androidx.test.runner.screenshot.BasicScreenCaptureProcessor;
+import androidx.test.runner.screenshot.ScreenCapture;
+import androidx.test.runner.screenshot.ScreenCaptureProcessor;
+import androidx.test.runner.screenshot.Screenshot;
+
+import static androidx.test.core.app.ApplicationProvider.getApplicationContext;
+
+@NotNullByDefault
+public class ScreenshotOnFailureRule implements TestRule {
+
+	FailureHandler defaultFailureHandler =
+			new DefaultFailureHandler(getApplicationContext());
+
+	@Override
+	public Statement apply(Statement base, Description description) {
+		HashSet<ScreenCaptureProcessor> processors = new HashSet<>(1);
+		processors.add(new BasicScreenCaptureProcessor());
+		Screenshot.addScreenCaptureProcessors(processors);
+		return new Statement() {
+			@Override
+			public void evaluate() throws Throwable {
+				AtomicBoolean errorHandled = new AtomicBoolean(false);
+				Espresso.setFailureHandler((throwable, matcher) -> {
+					takeScreenshot(description);
+					errorHandled.set(true);
+					defaultFailureHandler.handle(throwable, matcher);
+				});
+				try {
+					base.evaluate();
+				} catch (Throwable t) {
+					if (!errorHandled.get()) {
+						takeScreenshot(description);
+					}
+					throw t;
+				}
+			}
+		};
+	}
+
+	private void takeScreenshot(Description description) {
+		String name = description.getTestClass().getSimpleName();
+		ScreenCapture capture = Screenshot.capture();
+		capture.setName(name);
+		try {
+			capture.process();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+}

briar-android/src/androidTest/java/org/briarproject/briar/android/UiTest.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.briar.R;
+import org.junit.ClassRule;
 
 import javax.inject.Inject;
 
@@ -23,6 +24,10 @@ import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_
 @SuppressWarnings("WeakerAccess")
 public abstract class UiTest {
 
+	@ClassRule
+	public static final ScreenshotOnFailureRule screenshotOnFailureRule =
+			new ScreenshotOnFailureRule();
+
 	protected final String USERNAME =
 			getApplicationContext().getString(R.string.screenshot_alice);
 	protected static final String PASSWORD = "123456";