WebView Test Instructions

Android Instructions

Please follow the instructions at android_test_instructions.md. This guide is an extension with WebView-specific content.

Note: except where otherwise noted, all tests require a device or emulator.

Chromium-side tests

Instrumentation tests

These tests live under //android_webview/javatests/, and are mostly end-to-end (with the exception of the //android_webview/glue/ layer).

# Build
$ autoninja -C out/Default webview_instrumentation_test_apk

# Run tests (any of these commands):
$ out/Default/bin/run_webview_instrumentation_test_apk # All tests
$ out/Default/bin/run_webview_instrumentation_test_apk -f AwContentsTest#* # A particular test suite
$ out/Default/bin/run_webview_instrumentation_test_apk -f AwContentsTest#testClearCacheInQuickSuccession # A single test
$ out/Default/bin/run_webview_instrumentation_test_apk -f AwContentsTest#*Succession # Any glob pattern matching 1 or more tests

# Print both Java and C++ log messages to the console (optional):
$ adb logcat
You can optionally use ClassName.methodName instead of ClassName#methodName; the chromium test runner understands either syntax.

Java unittests

These tests live under //android_webview/junit/ and use Robolectric.

Tip: Robolectric tests run on workstation and do not need a device or emulator. These generally run much faster than on-device tests.
# Build
$ autoninja -C out/Default android_webview_junit_tests

# Run tests (any of these commands):
$ out/Default/bin/run_android_webview_junit_tests # All tests
$ out/Default/bin/run_android_webview_junit_tests -f *FindAddressTest#* # Same glob patterns work here

# Print both Java and C++ log messages to the console (optional) by passing "-v"
# to the test runner. Example:
$ out/Default/bin/run_android_webview_unittests -v # All tests, including logs
For junit tests, filter (-f) arguments require fully qualified class names (e.g. org.chromium.android_webview.robolectric.FindAddressTest), but replacing the package name with a glob wildcard (*), as in the example above, will work if the class name is unique.

Native unittests

These are any *_test.cc or *_unittest.cc test under //android_webview/. Currently, we only have tests under //android_webview/browser/ and //android_webview/lib/.

# Build
$ autoninja -C out/Default android_webview_unittests

# Run tests (any of these commands):
$ out/Default/bin/run_android_webview_unittests # All tests
$ out/Default/bin/run_android_webview_unittests -f AndroidStreamReaderURLRequestJobTest.* # Same glob patterns work here

# Print both Java and C++ log messages to the console (optional):
$ adb logcat

Layout tests and page cycler tests

WebView's layout tests and page cycler tests exercise the WebView installed on the system and instrument the system WebView shell app (system_webview_shell_apk). These test cases are defined in //android_webview/tools/system_webview_shell/.

Important: these tests compile and install both system_webview_apk and system_webview_shell_apk.

You will need to configure GN args to make sure system_webview_apk is a valid WebView provider for your system. Please see the full build instructions.

If you are using an emulator, you will also need to configure the system_webview_shell_package_name GN arg. See WebView shell docs for details.

# Build (this also compiles system_webview_shell_apk and system_webview_apk)
$ autoninja -C out/Default system_webview_shell_layout_test_apk

# Run layout tests (installs the test APK, WebView shell, and
# system_webview_apk, and also switches your WebView provider)
$ out/Default/bin/run_system_webview_shell_layout_test_apk

# Print both Java and C++ log messages to the console (optional):
$ adb logcat

To run page cycler tests instead, use the system_webview_shell_page_cycler_apk target and test runner in the steps above.

UI tests

Like layout and page cycler tests, WebView UI tests use the WebView installed on the system (and will automatically compile and install the system_webview_apk target). Unlike those tests however, this test suite does not depend on the system WebView shell app, so the setup is simpler. You will still need to follow the full build instructions to correctly configure the system_webview_apk target, but will not need to worry about compiling the WebView shell (and do not need to worry about https://crbug.com/1205665).

# Build (this also compiles system_webview_apk)
$ autoninja -C out/Default webview_ui_test_app_test_apk

# Run layout tests (installs the test APK and system_webview_apk and also
# switches your WebView provider)
$ out/Default/bin/run_webview_ui_test_app_test_apk

# Print both Java and C++ log messages to the console (optional):
$ adb logcat

Useful test runner options

Debugging flaky tests

$ out/Default/bin/run_webview_instrumentation_test_apk \ # Any test runner
    --num_retries=0 \ # Tests normally retry-on-failure; disable for easier repo
    --repeat=100 \ # Repeat up to 100 times for a failure
    --break-on-failure \ # Stop repeating once we see the first failure

Enable a Feature for a local run

$ out/Default/bin/run_webview_instrumentation_test_apk \ # Any test runner
    # Desired Features; see commandline-flags.md for more information
    --enable-features="MyFeature,MyOtherFeature" \

Debugging hangs in instrumentation tests

If an instrumentation test is hanging, it's possible to get a callstack from the browser process. This requires running on a device with root.

It's not possible to get a callstack from the renderer because the sandbox will prevent the trace file from being written. A workaround if you want to see the renderer threads is to run in single-process mode by adding @OnlyRunIn(SINGLE_PROCESS) above the test.

(shell)in your workstation's shell
(phone)inside the phone's shell which you entered through adb shell
# Find the pid
$ (shell) adb root
$ (shell) adb shell

# Get the main WebView Shell pid, e.g. org.chromium.android_webview.shell and
# not org.chromium.android_webview.shell:sandboxed_process0
$ (phone) ps -A | grep org.chromium.android_webview.shell
# Generate a callstack (this won't kill the process)
$ (phone) kill -3 pid
# Look for the latest trace
$ (phone) ls /data/anr/ -l
# Copy the trace locally
$ (shell) adb pull /data/anr/trace_01 /tmp/t1
# Generate a callstack. Run this from the source directory.
$ (shell) third_party/android_platform/development/scripts/stack --output-directory=out/Release /tmp/t1

External tests

As WebView is an Android system component, we have some tests defined outside of the chromium repository, but which the team still maintains. For some of these tests, we have scripts to help chromium developers check these tests.

All of these tests are end-to-end, so they exercise whatever WebView implementation you've installed and selected on your device. This also means you can enable Features and commandline flags the same way as you would for production.


WebView has CTS tests, testing end-to-end behavior (using the WebView installed on the system). These tests live in the Android source tree (under //platform/cts/tests/tests/webkit/).

Chromium developers can download and run pre-built APKs for these test cases with:

# Install the desired WebView APK

# Run pre-built WebView CTS tests:
$ android_webview/tools/run_cts.py \
    --verbose \ # Optional
    -f=android.webkit.cts.WebViewTest#* # Supports similar test filters

# Print both Java and C++ log messages to the console (optional):
$ adb logcat
Tip: make sure your device locale is English (United States) per CTS setup requirements.

To disable failing CTS tests, please see the cts_config README file.

If you'd like to edit these tests, see internal documentation at http://go/clank-webview for working with Android checkouts.

AndroidX (Support Library)

WebView also has an AndroidX module, which has its own tests (similar to CTS tests). These tests live under the AOSP source tree, under //platform/frameworks/support/.

TODO(ntfschr): document the solution for https://crbug.com/891102, when that's fixed.