--- a/toolkit/components/telemetry/tests/unit/test_TelemetryEvents_buildFaster.js
+++ b/toolkit/components/telemetry/tests/unit/test_TelemetryEvents_buildFaster.js
@@ -1,19 +1,123 @@
 /* Any copyright is dedicated to the Public Domain.
    http://creativecommons.org/publicdomain/zero/1.0/
 */
 
+ChromeUtils.import("resource://services-common/utils.js");
+
+/**
+ * Return the path to the definitions file for the events.
+ */
+function getDefinitionsPath() {
+  // Write the event definition to the spec file in the binary directory.
+  let definitionFile = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+  definitionFile = Services.dirsvc.get("GreD", Ci.nsIFile);
+  definitionFile.append("EventArtifactDefinitions.json");
+  return definitionFile.path;
+}
+
+add_task(async function test_setup() {
+  do_get_profile();
+});
+
+add_task({
+    // The test needs to write a file, and that fails in tests on Android.
+    // We don't really need the Android coverage, so skip on Android.
+    skip_if: () => AppConstants.platform == "android"
+  }, async function test_invalidJSON() {
+  const INVALID_JSON = "{ invalid,JSON { {1}";
+  const FILE_PATH = getDefinitionsPath();
+
+  // Write a corrupted JSON file.
+  await OS.File.writeAtomic(FILE_PATH, INVALID_JSON, { encoding: "utf-8", noOverwrite: false });
+
+  // Simulate Firefox startup. This should not throw!
+  await TelemetryController.testSetup();
+  await TelemetryController.testPromiseJsProbeRegistration();
+
+  // Cleanup.
+  await TelemetryController.testShutdown();
+  await OS.File.remove(FILE_PATH);
+});
+
+add_task({
+    // The test needs to write a file, and that fails in tests on Android.
+    // We don't really need the Android coverage, so skip on Android.
+    skip_if: () => AppConstants.platform == "android"
+  }, async function test_dynamicBuiltin() {
+  const DYNAMIC_EVENT_SPEC =  {
+    "telemetry.test.builtin": {
+      "test": {
+        "objects": [
+          "object1",
+          "object2"
+        ],
+        "expired": false,
+        "methods": [
+          "test1",
+          "test2"
+        ],
+        "extra_keys": [
+          "key2",
+          "key1"
+        ],
+        "record_on_release": false
+      }
+    }
+  };
+
+  Telemetry.clearEvents();
+
+  // Let's write to the definition file to also cover the file
+  // loading part.
+  const FILE_PATH = getDefinitionsPath();
+  await CommonUtils.writeJSON(DYNAMIC_EVENT_SPEC, FILE_PATH);
+
+  // Start TelemetryController to trigger loading the specs.
+  await TelemetryController.testReset();
+  await TelemetryController.testPromiseJsProbeRegistration();
+
+  // Record the events
+  const TEST_EVENT_NAME = "telemetry.test.builtin";
+  Telemetry.recordEvent(TEST_EVENT_NAME, "test1", "object1");
+  Telemetry.recordEvent(TEST_EVENT_NAME, "test2", "object1", null,
+                        {"key1": "foo", "key2": "bar"});
+  Telemetry.recordEvent(TEST_EVENT_NAME, "test2", "object2", null,
+                        {"key2": "bar"});
+
+  // Check the values we tried to store.
+  const snapshot =
+    Telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, false);
+  Assert.ok(("parent" in snapshot), "Should have parent events in the snapshot.");
+
+  let expected = [
+    [TEST_EVENT_NAME, "test1", "object1"],
+    [TEST_EVENT_NAME, "test2", "object1", null, {key1: "foo", key2: "bar"}],
+    [TEST_EVENT_NAME, "test2", "object2", null, {key2: "bar"}],
+  ];
+  let events = snapshot.parent;
+  Assert.equal(events.length, expected.length, "Should have recorded the right amount of events.");
+  for (let i = 0; i < expected.length; ++i) {
+    Assert.deepEqual(events[i].slice(1), expected[i],
+                     "Should have recorded the expected event data.");
+  }
+
+  // Clean up.
+  await TelemetryController.testShutdown();
+  await OS.File.remove(FILE_PATH);
+});
+
 add_task(async function test_dynamicBuiltinEvents() {
   Telemetry.clearEvents();
   Telemetry.canRecordExtended = true;
 
   const TEST_EVENT_NAME = "telemetry.test.dynamicbuiltin";
 
-  // Register some dynbamic builtin test events.
+  // Register some dynamic builtin test events.
   Telemetry.registerBuiltinEvents(TEST_EVENT_NAME, {
     // Event with only required fields.
     "test1": {
       methods: ["test1"],
       objects: ["object1"],
     },
     // Event with extra_keys.
     "test2": {