To start the tests, run the following command in the mozilla-build shell, at the top level of your obj-dir:
./mach mochitest-metro (old way was To run a single test file or directory, pymake ./mach mochitest-metro-chrome)path/to/test/file.js
The Metro browser will launch, run the tests and exit. Any failures will be printed to the console. The complete test log will be written to the file <code>mochitest-metro-chrome.log</code> in the objdir.