Update the docs and examples to the GleanTestRule

docs/user/experiments-api.md

@@ -26,7 +26,6 @@ There are test APIs available too:
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.SearchDefault
 
-Glean.enableTestingMode()
 // Was the experiment annotated in Glean pings?
 assertTrue(Glean.testIsExperimentActive("blue-button-effective"))
 // Was the correct branch reported?

docs/user/metrics/boolean.md

@@ -28,7 +28,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Flags
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Flags.a11yEnabled.testHasValue())

docs/user/metrics/counter.md

@@ -28,7 +28,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Controls
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Controls.refreshPressed.testHasValue())

docs/user/metrics/datetime.md

@@ -46,7 +46,6 @@ There are test APIs available too.
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Install
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Install.firstRun.testHasValue())

docs/user/metrics/event.md

@@ -33,7 +33,6 @@ There are test APIs available too, for example:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Views
-Glean.enableTestingMode()
 
 // Was any event recorded?
 assertTrue(Views.loginOpened.testHasValue())

docs/user/metrics/labeled_counters.md

@@ -32,7 +32,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Stability
-Glean.enableTestingMode()
 // Was anything recorded?
 assertTrue(Stability.crashCount["uncaught_exception"].testHasValue())
 assertTrue(Stability.crashCount["native_code_crash"].testHasValue())

docs/user/metrics/labeled_strings.md

@@ -31,7 +31,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Login
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Login.errorsByStage["server_auth"].testHasValue())

docs/user/metrics/string.md

@@ -26,7 +26,7 @@ search.default:
     ...
 ```
 
-## API 
+## API
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.SearchDefault
@@ -42,7 +42,6 @@ There are test APIs available too:
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.SearchDefault
 
-Glean.enableTestingMode()
 // Was anything recorded?
 assertTrue(SearchDefault.name.testHasValue())
 // Does the string metric have the expected value?

docs/user/metrics/string_list.md

@@ -40,7 +40,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Search
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Search.engines.testHasValue())

docs/user/metrics/timespan.md

@@ -59,7 +59,6 @@ There are test APIs available too:
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Auth
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(Auth.loginTime.testHasValue())

docs/user/metrics/timing_distribution.md

@@ -58,7 +58,6 @@ Continuing the `pageLoad` example above, at this point the metric should have a
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.Pages
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(pages.pageLoad.testHasValue())
@@ -76,7 +75,7 @@ assertEquals(2L, snapshot.count())
 ## Limits
 
 * Which range of values is recorded in detail depends on the `time_unit`, e.g. for milliseconds, all values greater 60000 are recorded as overflow values.
-  
+
 ## Examples
 
 * How long does it take a page to load?

docs/user/metrics/uuid.md

@@ -31,11 +31,10 @@ There are test APIs available too.
 
 ```Kotlin
 import org.mozilla.yourApplication.GleanMetrics.User
-Glean.enableTestingMode()
 
 // Was anything recorded?
 assertTrue(User.clientId.testHasValue())
-// Was it the expected value? 
+// Was it the expected value?
 assertEquals(uuid, User.clientId.testGetValue())
 ```
 
@@ -50,7 +49,7 @@ assertEquals(uuid, User.clientId.testGetValue())
 ## Recorded errors
 
 * None.
- 
+
 ## Reference
 
 * See [Kotlin API docs](../../../javadoc/glean/mozilla.telemetry.glean.private/-uuid-metric-type/index.html).

docs/user/pings/testing-custom-pings.md

@@ -101,40 +101,30 @@ import my.component.GleanMetrics.CustomPingData
 import org.mockito.Mockito.spy
 import org.mockito.Mockito.`when`
 
-/**
- * This is an helper function used to enable testing mode for Glean.
- * Should only be called once before the tests, but nothing breaks if it's
- * called more than once!
- */
-fun setupGleanOnce() {
-  // Enable testing mode
-  // (Perhaps called from a @Before method so it precedes every test in the suite.)
-  Glean.enableTestingMode()
+@RunWith(AndroidJUnit4::class)
+class MyCustomPingSchedulerTest {
+    // Apply the GleanTestRule
+    @get:Rule
+    val gleanRule = GleanTestRule(ApplicationProvider.getApplicationContext())
 
-  // We're using the WorkManager in a bunch of places, and Glean will crash
-  // in tests without this line. Let's simply put it here.
-  WorkManagerTestInitHelper.initializeTestWorkManager(context)
+    @Test
+    fun `verify custom ping metrics`() {
+      setupGleanOnce()
 
-  Glean.initialize(context)
-}
+      val scheduler = spy(MyCustomPingScheduler())
+      doAnswer {
+        // Here we validate the content that goes into the ping.
+        assertTrue(CustomPingData.sampleString.testHasValue())
+        assertEquals("test-data", CustomPingData.sampleString.testGetValue())
 
-@Test
-fun `verify custom ping metrics`() {
-  setupGleanOnce()
+        // We want to intercept this call, but we also want to make sure the
+        // real Glean API is called in order to clear the ping store and to provide
+        // consistent behaviour with respect to the application.
+        it.callRealMethod()
+      }.`when`(scheduler).sendPing()
 
-  val scheduler = spy(MyCustomPingScheduler())
-  doAnswer {
-    // Here we validate the content that goes into the ping.
-    assertTrue(CustomPingData.sampleString.testHasValue())
-    assertEquals("test-data", CustomPingData.sampleString.testGetValue())
-
-    // We want to intercept this call, but we also want to make sure the
-    // real Glean API is called in order to clear the ping store and to provide
-    // consistent behaviour with respect to the application.
-    it.callRealMethod()
-  }.`when`(scheduler).sendPing()
-
-  scheduler.addSomeData()
-  scheduler.schedulePing()
+      scheduler.addSomeData()
+      scheduler.schedulePing()
+    }
 }
 ```

docs/user/testing-metrics.md

@@ -6,7 +6,21 @@ These functions expose a way to inspect and validate recorded metric values with
 
 ## General test API method semantics
 
-In order to prevent issues with async calls when unit testing Glean, it is important to put the Glean SDK into testing mode by calling `Glean.enableTestingMode()`.
+In order to prevent issues with async calls when unit testing Glean, it is important to put the Glean SDK into testing mode by applying the JUnit `GleanTestRule` to your test class, as shown below:
+
+```kotlin
+@RunWith(AndroidJUnit4::class)
+class ActivityCollectingDataTest {
+    // Apply the GleanTestRule
+    @get:Rule
+    val gleanRule = GleanTestRule(ApplicationProvider.getApplicationContext())
+
+    fun checkCollectedData() {
+      // The Glean SDK testing API can be called here.
+    }
+}
+```
+
 This will ensure that metrics are done recording when the other test functions are used.
 
 To check if a value exists (i.e. it has been recorded), there is a `testHasValue()` function on each of the metric instances:
@@ -43,10 +57,6 @@ GleanMetrics.Foo.UriCount.testGetValue("customPing")
 
 Here is a longer example to better illustrate the intended use of the test API:
 ```kotlin
-// Enable testing mode
-// (Perhaps called from a @Before method so it precedes every test in the suite.)
-Glean.enableTestingMode()
-
 // Record a metric value with extra to validate against
 GleanMetrics.BrowserEngagement.click.record(
     mapOf(