android_test_instructions.md: Mention autotest.py and --list-tests

Bug: 1347537
Change-Id: Ie751611bc5aa52fa7c00be34d5aafe17709657be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3788451
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Benjamin Joyce <bjoyce@chromium.org>
Commit-Queue: Benjamin Joyce <bjoyce@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1029330}

docs/android_build_instructions.md

@@ -359,7 +359,7 @@ for more on debugging, including how to debug Java code.
 ### Testing
 
 For information on running tests, see
-[Android Test Instructions](testing/android_test_instructions.md).
+[Android Test Instructions](/testing/android/docs/README.md)
 
 ### Faster Edit/Deploy
 

testing/android/docs/android_test_instructions.md

@@ -99,6 +99,16 @@ Java test files vary a bit more widely than their C++ counterparts:
 Once you know what to build, just do it like you normally would build anything
 else, e.g.: `ninja -C out/Release chrome_public_test_apk`
 
+### Determining Test Target
+
+If you do not know what target a test file belongs to, you can use
+`//tools/autotest.py` to figure it out fo you:
+
+```sh
+# Builds relevant test target and then runs the test:
+tools/autotest.py -C <output directory> TestClassName
+```
+
 ## Running Tests
 
 All functional tests should be runnable via the wrapper scripts generated at
@@ -115,6 +125,18 @@ The commands used by the buildbots are printed in the logs. Look at
 https://build.chromium.org/ to duplicate the same test command as a particular
 builder.
 
+### Listing Available Tests
+
+Use `--list-tests` to list what tests are available.
+
+```sh
+# Prints out all available tests:
+<output directory>/bin/run_<target_name> --list-tests
+
+# Prints out all available tests that match a filter:
+<output directory>/bin/run_<target_name> --list-tests -f "*MyFilter*"
+```
+
 ### INSTALL\_FAILED\_CONTAINER\_ERROR or INSTALL\_FAILED\_INSUFFICIENT\_STORAGE
 
 If you see this error when the test runner is attempting to deploy the test