Android code coverage instructions

This is instruction for code coverage for android instrumentation and junit tests.

How EMMA coverage works

In order to use EMMA code coverage, we need to create build time .em file and runtime .ec file. Then we need to process them using the build/android/generate_emma_html.py script.

How to collect EMMA coverage data

1. Build your APK with the GN arg emma_coverage=true.

   gn args out-gn/Debug
   > target_os = "android"
   > emma_coverage = true
   

   By doing so, .em files will be created in out-gn/Debug.
2. Run tests, with option --coverage-dir <directory>, to specify where to save the .ec file. For example, you can run chrome junit tests: out-gn/Debug/bin/run_chrome_junit_tests --coverage-dir /tmp/coverage.
3. Now we have both .em and .ec files. We can merge them and create a html file, using generate_emma_html.py. For example, generate_emma_html.py can be called this way: build/android/generate_emma_html.py --coverage-dir /tmp/coverage/ --metadata-dir out-gn/Debug/ --output example.html. Then an example.html containing coverage info will be created: EMMA: writing [html] report to [<your_current_directory>/example.html] …