Android: add documentation about junit tests.

docs/android_test_instructions.md

Index: docs/android_test_instructions.md
diff --git a/docs/android_test_instructions.md b/docs/android_test_instructions.md
index 2129cadde9166cfc8effa383f2ec092c745bde4c..fdc65d85497eee252e912e7654ef3420aa1b262c 100644
--- a/docs/android_test_instructions.md
+++ b/docs/android_test_instructions.md
@@ -124,7 +124,9 @@ If you build in an output directory other than "out", you may have to tell
 test\_runner.py where you place it. Say you build your android code in
 out\_android, then do `export CHROMIUM_OUT_DIR=out_android` before running the
 command below. You have to do this even if your "out" directory is a symlink
-pointing to "out_android".
+pointing to "out_android". You can also use ```--output-directory``` to point

[dgn, 2015/10/22 18:09:23]

I think triple backtick make a new paragraph. Did you check how the file is
rendered on gitiles? 

[mlamouri (slow - plz ping), 2015/10/23 13:20:10]

No.
I did try on gitiles in case of it was a gitiles oddities. I'm glad it's not :)

[Bernhard Bauer, 2015/10/23 15:20:21]

But if you only want code markup, single backticks are still sufficient.

[dgn, 2015/10/26 10:12:05]

It would also be consistent with the code in the rest of the file, that uses
single backticks

+to the path of your output directory, for example,
+```--output-directory=out_android/Debug```.
 
 ## INSTALL\_FAILED\_CONTAINER\_ERROR or INSTALL\_FAILED\_INSUFFICIENT\_STORAGE
 
@@ -149,6 +151,34 @@ traces, pipe the output through
 output directory other than "out", pass
 `--chrome-symbols-dir=out_directory/{Debug,Release}/lib` to the script as well.
 
+## Junit tests

[Bernhard Bauer, 2015/10/22 16:19:12]

Nit: JUnit (capital U) here and elsewhere.

[mlamouri (slow - plz ping), 2015/10/23 13:20:10]

Done.

+
+Junit tests are Java unittests running on the host instead of the target device.
+They are faster to run and therefore are recommended over instrumentation tests
+when possible.
+
+There are two junit test suites: ```content_junit_tests``` and
+```chrome_junit_tests```.

[Bernhard Bauer, 2015/10/22 16:19:12]

There are more JUnit test suites than that, e.g. base_junit_tests,
components_junit_tests, net_junit_tests, ...

[dgn, 2015/10/22 18:09:23]

I wish there was a unified junit target with all the tests... It's not like it's
going to take as long as the instrumentation tests to build and run

[mlamouri (slow - plz ping), 2015/10/23 13:20:10]

Changed to mention content_junit_tests and chrome_junit_tests as examples.

+
+When adding a new junit test, the associated ```BUILD.gn``` file need to be
+updated. For ```chrome_junit_tests```, this is ```chrome/android/BUILD.gn``` and
+for ```content_junit_tests```, this is ```content/public/android/BUILD.gn```.
+
+```shell
+# Build the test suite.
+ninja -C out/Release content_junit_tests
+ninja -C out/Release chrome_junit_tests
+
+# Run the test suite.
+build/android/test_runner.py junit -s content_junit_tests --release -vvv
+build/android/test_runner.py junit -s chrome_junit_tests --release -vvv
+
+# Run a subset of tests. Contrary to gtests and instrumentation tests, the
+entire package name has to be used.

[dgn, 2015/10/22 18:09:23]

Not true. This is working for me:  net_junit_tests -f "*testGetNextAuthToken"   

[mlamouri (slow - plz ping), 2015/10/23 13:20:10]

Made the comment less assertive.

[Bernhard Bauer, 2015/10/23 15:20:21]

I think the full package name is matched against the filter, which would explain
the behavior Nicolas is seeing ☺

+build/android/test_runner.py junit -s chrome_junit_tests --release -vvv
+-f "org.chromium.chrome.browser.media.*"
+```
+
 ## Gtests
 
 ```shell