Fix CustomTabsTest intent resolution with ActivityScenario

ActivityScenario.launch resolves intents through normal Android routing,
so an ACTION_VIEW intent with an HTTP URL resolved to Chrome rather than
IntentReceiverActivity. Set the component explicitly before launching to
force the activity within the test process.

Improve error message when BrowserActivityTestRule.activity is unavailable

Author: rvandermeulen

app/src/androidTest/java/org/mozilla/reference/browser/helpers/BrowserActivityTestRule.kt

@@ -29,7 +29,7 @@ class BrowserActivityTestRule : ExternalResource() {
         get() {
             var result: BrowserActivity? = null
             scenario.onActivity { result = it }
-            return result!!
+            return checkNotNull(result) { "Activity unavailable — scenario may be in a terminal state" }
         }
 
     override fun before() {

app/src/androidTest/java/org/mozilla/reference/browser/ui/CustomTabsTest.kt

@@ -4,7 +4,9 @@
 
 package org.mozilla.reference.browser.ui
 
+import android.content.ComponentName
 import androidx.test.core.app.ActivityScenario
+import androidx.test.platform.app.InstrumentationRegistry
 import mockwebserver3.MockWebServer
 import org.junit.After
 import org.junit.Before
@@ -28,6 +30,19 @@ class CustomTabsTest {
     @JvmField
     val retryTestRule = RetryTestRule(3)
 
+    // ActivityScenario.launch resolves intents via normal Android routing, so an ACTION_VIEW
+    // intent with an HTTP URL would resolve to the browser rather than IntentReceiverActivity.
+    // Setting the component explicitly forces it to launch within the test process.
+    private fun launchCustomTab(pageUrl: String) =
+        ActivityScenario.launch<IntentReceiverActivity>(
+        createCustomTabIntent(pageUrl).apply {
+            component = ComponentName(
+                InstrumentationRegistry.getInstrumentation().targetContext,
+                IntentReceiverActivity::class.java,
+            )
+        },
+    )
+
     @Before
     fun setUp() {
         mockWebServer = MockWebServer().apply {
@@ -45,10 +60,7 @@ class CustomTabsTest {
     fun openCustomTabTest() {
         val customTabPage = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(customTabPage.url.toString()),
-        ).use {
+        launchCustomTab(customTabPage.url.toString()).use {
             customTabScreen {
                 verifyCloseButton()
                 verifyTrackingProtectionIcon()
@@ -65,10 +77,7 @@ class CustomTabsTest {
     fun verifyCustomTabMenuItemsTest() {
         val customTabPage = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(customTabPage.url.toString()),
-        ).use {
+        launchCustomTab(customTabPage.url.toString()).use {
             customTabScreen {
             }.openMainMenu {
                 verifyForwardButton()
@@ -87,10 +96,7 @@ class CustomTabsTest {
         val pageLinks = TestAssetHelper.getGenericAsset(mockWebServer, 4)
         val genericURL = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(pageLinks.url.toString()),
-        ).use {
+        launchCustomTab(pageLinks.url.toString()).use {
             customTabScreen {
                 clickGenericLink("Link 1")
                 verifyPageTitle(genericURL.title)
@@ -110,10 +116,7 @@ class CustomTabsTest {
     fun customTabShareTest() {
         val customTabPage = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(customTabPage.url.toString()),
-        ).use {
+        launchCustomTab(customTabPage.url.toString()).use {
             customTabScreen {
             }.openMainMenu {
             }.clickShareButton {
@@ -126,10 +129,7 @@ class CustomTabsTest {
     fun customTabRequestDesktopSiteTest() {
         val customTabPage = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(customTabPage.url.toString()),
-        ).use {
+        launchCustomTab(customTabPage.url.toString()).use {
             customTabScreen {
             }.openMainMenu {
                 switchRequestDesktopSiteToggle()
@@ -146,10 +146,7 @@ class CustomTabsTest {
     fun customTabOpenInBrowserTest() {
         val customTabPage = TestAssetHelper.getGenericAsset(mockWebServer, 1)
 
-        ActivityScenario
-            .launch<IntentReceiverActivity>(
-            createCustomTabIntent(customTabPage.url.toString()),
-        ).use {
+        launchCustomTab(customTabPage.url.toString()).use {
             customTabScreen {
             }.openMainMenu {
             }.clickOpenInBrowserButton {