My initial attempt was to add a new <activity> in chrome/android/javatests/AndroidManifest.xml.

    <activity android:name="org.chromium.chrome.test.ui.SimpleUiActivity"            
        android:exported="true"/>

I first had issues with writing an ActivityTestRule that would actually trigger the new activity.  Despite setting the class name in getActivityIntent, it would be overwritten in launchActivity.

I could start it manually from the command line via:
    adb shell am start -n org.chromium.chrome.tests/org.chromium.chrome.test.ui.SimpleUiActivity

I had to add a hack to stash the intent and overwrite the class name again in beforeActivityLaunched.

At that point, it complained about the activity being in a different process, so I needed hardcode the process:

    <activity android:name="org.chromium.chrome.test.ui.SimpleUiActivity"
        android:process="{{manifest_package}}"
        android:exported="true"/>

Now the activity was being launched, but it was crashing because it never returned to idle within 45 seconds.  At that point, I gave up.

We might need to add a new <instrumentation> attribute pointing to the test package or something to allow such a crazy thing.

+jbudorick

Sending to Ted for triage.

I messed around with this some earlier this week -- convincing the OS to load an Activity defined in the test package from within the app package is going to be tricky.

Solutions here will probably involve either:
 - a separate suite
 - merging the test APK and the app APK

I think this might be easier with JUnit 4 tests? At least it should be possible to use an ActivityTestRule that launches a custom SimpleUiActivity.

Bulk edit: Moving back into the untriaged pool, as I'm leaving the project.

Sorry I might miss something but why add this SimpleUiActivity in test package, as org.chromium.chrome.tests?
Would that be easier if we add it in app package or some isolated application if don't want to affect current chrome app, and launch with ActivityTestRule? 

@yliuyliu, I'm definitely OK with this being in a different package/application.  We just didn't want this to be part of the shipping Chrome app.

With it being in the same test package, the thinking was that it would create one fewer things to test/be tested on the bots.  It would be part of existing workflows and thus be easier to adopt.  If we found that isn't feasible, I think we could look at moving it elsewhere, but I think the ideal case is that it would work within the existing test packages/APKs.

Seems this became much easier to implement after test APK and app APK merged into just one apk, ChromePublicTest.apk, with all chrome app libraries and no package difference.
We can simply add one basic activity in javatests/AndroidManifest.xml to skip native and skip Chrome browser initialization to just attach UI components for testing.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0

commit b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0
Author: Yun Liu <yliuyliu@google.com>
Date: Wed Jan 09 23:06:26 2019

Add DummyUiActivity for testing UI components without accessing native


Bug: 728297
Change-Id: Iaa573cb32e624544dcf5a1fdbdc9215505596574
Reviewed-on: https://chromium-review.googlesource.com/c/1356593
Commit-Queue: Yun Liu <yliuyliu@google.com>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621357}
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java/src/org/chromium/chrome/browser/download/home/DownloadManagerCoordinatorImpl.java
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java/src/org/chromium/chrome/browser/download/home/list/UiUtils.java
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java/src/org/chromium/chrome/browser/download/home/toolbar/ToolbarCoordinator.java
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java/src/org/chromium/chrome/browser/download/home/toolbar/ToolbarUtils.java
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java/src/org/chromium/chrome/browser/download/ui/DownloadManagerUi.java
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/java_sources.gni
[modify] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/javatests/AndroidManifest.xml
[add] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/javatests/src/org/chromium/chrome/browser/download/home/DownloadActivityV2Test.java
[add] https://crrev.com/b70ea5992740bfa0ddb87c244b47f31d9b8d1dc0/chrome/android/javatests/src/org/chromium/chrome/test/ui/DummyUiActivity.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/84ad844a557d24efd260cfd5afb177799a40cabc

commit 84ad844a557d24efd260cfd5afb177799a40cabc
Author: Yun Liu <yliuyliu@google.com>
Date: Thu Jan 17 20:50:27 2019

Move DisableAnimationsTestRule to test/ui and add base DummyUiActivityTestCase for DummyUiActivity


Bug: 728297
Change-Id: I5945bb2abaef870e10f60f82b0ff41dab116cd00
Reviewed-on: https://chromium-review.googlesource.com/c/1415771
Commit-Queue: Yun Liu <yliuyliu@google.com>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623833}
[modify] https://crrev.com/84ad844a557d24efd260cfd5afb177799a40cabc/chrome/android/java_sources.gni
[modify] https://crrev.com/84ad844a557d24efd260cfd5afb177799a40cabc/chrome/android/javatests/src/org/chromium/chrome/browser/download/DownloadActivityTest.java
[modify] https://crrev.com/84ad844a557d24efd260cfd5afb177799a40cabc/chrome/android/javatests/src/org/chromium/chrome/browser/download/home/DownloadActivityV2Test.java
[rename] https://crrev.com/84ad844a557d24efd260cfd5afb177799a40cabc/chrome/android/javatests/src/org/chromium/chrome/test/ui/DisableAnimationsTestRule.java
[add] https://crrev.com/84ad844a557d24efd260cfd5afb177799a40cabc/chrome/android/javatests/src/org/chromium/chrome/test/ui/DummyUiActivityTestCase.java