Fix flaky TabSearch mocha test.

This CL makes 3 changes:
(1) The TabSearch organization mocha tests check focus and blur. This in
turn depends on window activation, which is not guaranteed for
browser_tests. This CL moves the tests to be interactive_ui_tests

(2) This CL updates the mocha test documentation.

(3) This CL fixes a null reference that emitted spammy log messages in
the tests.

Bug: 360760963
Change-Id: I58863d647bd30b1eea2a4956fd83f6e5b2b5e4ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5805528
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1345319}

chrome/test/data/webui/tab_search/auto_tab_groups_page_test.ts

@@ -9,7 +9,7 @@ import {TabOrganizationError, TabOrganizationState, TabSearchApiProxyImpl, TabSe
 import {assertEquals, assertFalse, assertTrue} from 'chrome://webui-test/chai_assert.js';
 import {eventToPromise, isVisible, microtasksFinished} from 'chrome://webui-test/test_util.js';
 
-import {createTab} from './tab_search_test_data.js';
+import {createProfileData, createTab} from './tab_search_test_data.js';
 import {TestTabSearchApiProxy} from './test_tab_search_api_proxy.js';
 import {TestTabSearchSyncBrowserProxy} from './test_tab_search_sync_browser_proxy.js';
 
@@ -23,6 +23,7 @@ suite('AutoTabGroupsPageTest', () => {
     document.body.innerHTML = window.trustedTypes!.emptyHTML;
 
     testApiProxy = new TestTabSearchApiProxy();
+    testApiProxy.setProfileData(createProfileData());
     const session = createSession();
     testApiProxy.setSession(session);
     TabSearchApiProxyImpl.setInstance(testApiProxy);
@@ -40,6 +41,7 @@ suite('AutoTabGroupsPageTest', () => {
     document.body.innerHTML = window.trustedTypes!.emptyHTML;
 
     testApiProxy = new TestTabSearchApiProxy();
+    testApiProxy.setProfileData(createProfileData());
     const session = createSession();
     testApiProxy.setSession(session);
     TabSearchApiProxyImpl.setInstance(testApiProxy);

chrome/test/data/webui/tab_search/tab_search_browsertest.cc

@@ -39,10 +39,6 @@ IN_PROC_BROWSER_TEST_F(TabSearchTest, MediaTabs) {
   RunTest("tab_search/tab_search_media_tabs_test.js", "mocha.run()");
 }
 
-IN_PROC_BROWSER_TEST_F(TabSearchTest, Organization) {
-  RunTest("tab_search/auto_tab_groups_page_test.js", "mocha.run()");
-}
-
 IN_PROC_BROWSER_TEST_F(TabSearchTest, Declutter) {
   RunTest("tab_search/declutter_page_test.js", "mocha.run()");
 }

chrome/test/data/webui/tab_search/tab_search_focus_test.cc

@@ -21,3 +21,9 @@ class TabSearchFocusTest : public WebUIMochaBrowserTest {
 IN_PROC_BROWSER_TEST_F(TabSearchFocusTest, MAYBE_App) {
   RunTest("tab_search/tab_search_page_focus_test.js", "mocha.run()");
 }
+
+// Some of the organization tests require checking focus and blur logic. This
+// must be run as an interactive_ui_test.
+IN_PROC_BROWSER_TEST_F(TabSearchFocusTest, Organization) {
+  RunTest("tab_search/auto_tab_groups_page_test.js", "mocha.run()");
+}

docs/testing_webui.md

@@ -329,3 +329,13 @@ IN_PROC_BROWSER_TEST_F(FooDialogBrowserTest, MyTest) {
       /*skip_test_loader=*/true));
 }
 ```
+
+### Common errors
+
+Tests that rely on focus, blur, or other input-related events need to be added
+to the interactive_ui_tests build target rather than the browser_tests target.
+browser_tests are run in parallel, and the window running the test will
+gain/lose activation at unpredictable times.
+
+Tests that touch production logic that depends on onFocus, onBlur or similar
+events also needs to be added to interactive_ui_tests