1 files changed, 36 insertions, 0 deletions
diff --git a/browser/components/syncedtabs/test/xpcshell/test_EventEmitter.js b/browser/components/syncedtabs/test/xpcshell/test_EventEmitter.js
new file mode 100644
index 0000000000..07f2a1b296
--- /dev/null
+++ b/browser/components/syncedtabs/test/xpcshell/test_EventEmitter.js
@@ -0,0 +1,36 @@
+"use strict";
+
+let { EventEmitter } = ChromeUtils.importESModule(
+  "resource:///modules/syncedtabs/EventEmitter.sys.mjs"
+);
+
+add_task(async function testSingleListener() {
+  let eventEmitter = new EventEmitter();
+  let spy = sinon.spy();
+
+  eventEmitter.on("click", spy);
+  eventEmitter.emit("click", "foo", "bar");
+  Assert.ok(spy.calledOnce);
+  Assert.ok(spy.calledWith("foo", "bar"));
+
+  eventEmitter.off("click", spy);
+  eventEmitter.emit("click");
+  Assert.ok(spy.calledOnce);
+});
+
+add_task(async function testMultipleListeners() {
+  let eventEmitter = new EventEmitter();
+  let spy1 = sinon.spy();
+  let spy2 = sinon.spy();
+
+  eventEmitter.on("some_event", spy1);
+  eventEmitter.on("some_event", spy2);
+  eventEmitter.emit("some_event");
+  Assert.ok(spy1.calledOnce);
+  Assert.ok(spy2.calledOnce);
+
+  eventEmitter.off("some_event", spy1);
+  eventEmitter.emit("some_event");
+  Assert.ok(spy1.calledOnce);
+  Assert.ok(spy2.calledTwice);
+});