Bug 1693025 - Expose a way to reset Glean in tests

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 [Full changelog](https://github.com/mozilla/glean.js/compare/v0.6.0...main)
 
+* [#143](https://github.com/mozilla/glean.js/pull/143): Provide a way to initialize and reset Glean.js in tests.
+
 # v0.6.0 (2021-03-22)
 
 * [#123](https://github.com/mozilla/glean.js/pull/123): BUGFIX: Fix support for ES6 environments.

glean/src/index/webext.ts

@@ -113,4 +113,26 @@ export default {
   unsetSourceTags(): void {
     Glean.unsetSourceTags();
   },
+
+  /**
+   * **Test-only API**
+   *
+   * Resets the Glean singleton to its initial state and re-initializes it.
+   *
+   * TODO: Only allow this function to be called on test mode (depends on Bug 1682771).
+   *
+   * @param applicationId The application ID (will be sanitized during initialization).
+   * @param uploadEnabled Determines whether telemetry is enabled.
+   *        If disabled, all persisted metrics, events and queued pings (except
+   *        first_run_date) are cleared. Default to `true`.
+   * @param config Glean configuration options.
+   * @returns A promise that resolves when the initialization is complete.
+   */
+  async testResetGlean(
+    applicationId: string,
+    uploadEnabled = true,
+    config?: ConfigurationInterface
+  ): Promise<void> {
+    return Glean.testResetGlean(applicationId, uploadEnabled, config);
+  }
 };

glean/tests/core/glean.spec.ts

@@ -412,4 +412,22 @@ describe("Glean", function() {
     await Glean.dispatcher.testBlockOnQueue();
     assert.strictEqual(Glean.sourceTags, undefined);
   });
+
+  it("testResetGlean correctly resets", async function () {
+    const metric = new StringMetricType({
+      category: "aCategory",
+      name: "aStringMetric",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    });
+
+    const TEST_VALUE = "TEST VALUE";
+    metric.set(TEST_VALUE);
+
+    assert.strictEqual(await metric.testGetValue(), TEST_VALUE);
+    await Glean.testResetGlean(testAppId);
+
+    assert.strictEqual(await metric.testGetValue(), undefined);
+  });
 });