Build Chromium webui test without rebuilding all browser_tests

Question

I added a simple JavaScript test to /src/chrome/test/data/webui/ and included the file in /src/chrome/chrome_tests.gypi.

I built it like this: ninja -C out/Debug browser_tests. That takes a while though. Is there a way to rebuild my test only, without also building all the other browser tests?

Answer 1

browser_tests is the only executable target to compile those tests so you need to use it in any case even if you perform a change in a single test. But you may want to try shared library compilation to improve the speed of your builds. For that just export GYP_DEFINES='component=shared_library' and then ./build/gyp_chromium before recompiling.

Answer 2

^{NOTE: This answer is not applicable to webui tests (they do not depend on test_data_dir_. Further, it is only relevant to Linux.}

Some test files is not compiled into browser_tests. For these cases, just set the CR_SOURCE_ROOT environment variable to the Chromium source directory, e.g. (if your Chromium source files are located at ~/chromium/src)

CR_SOURCE_ROOT=~/chromium/src/ ./out/Debug/browser_tests

I discovered this when I tried to figure out why the extension tests did not run. I started with looking up the error message in the source code:

Extension error: Could not load extension from ''. Manifest file is missing or unreadable.

After some debugging with gdb, I found that the test extension that is supposed to be loaded by ExtensionBrowserTest::LoadExtensionWithFlags did not load because the path was invalid. path was somehow set to "extensions/api_test/webrequest", and because this is not an absolute path, it was cleared in UnpackedInstaller::GetAbsolutePath by extension_path_ = base::MakeAbsoluteFilePath(extension_path_);.
Consequently, Chromium tries to load an extension from location "" (empty string), which obviously fails.

Ultimately, I tracked down the cause to test_data_dir_, which is initialized at DIR_TEST_DATA, which in turn is derived from DIR_SOURCE_ROOT, which in turn is read from the CR_SOURCE_ROOT environment variable. With the following command, my tests ran again, and I was able to update the extension tests without recompiling.

CR_SOURCE_ROOT=~/chromium/src/ ./out/Debug/browser_tests