1 files changed, 47 insertions, 0 deletions
diff --git a/cli/tests/workers_test.ts b/cli/tests/workers_test.ts
index 2c56a491c..bb00d67fd 100644
--- a/cli/tests/workers_test.ts
+++ b/cli/tests/workers_test.ts
@@ -184,3 +184,50 @@ Deno.test({
     await promise;
   },
 });
+
+Deno.test({
+  name: "worker is event listener",
+  fn: async function (): Promise<void> {
+    let messageHandlersCalled = 0;
+    let errorHandlersCalled = 0;
+
+    const promise1 = createResolvable();
+    const promise2 = createResolvable();
+
+    const worker = new Worker("../tests/subdir/event_worker.js", {
+      type: "module",
+    });
+
+    worker.onmessage = (_e: Event): void => {
+      messageHandlersCalled++;
+    };
+    worker.addEventListener("message", (_e: Event) => {
+      messageHandlersCalled++;
+    });
+    worker.addEventListener("message", (_e: Event) => {
+      messageHandlersCalled++;
+      promise1.resolve();
+    });
+
+    worker.onerror = (e): void => {
+      errorHandlersCalled++;
+      e.preventDefault();
+    };
+    worker.addEventListener("error", (_e: Event) => {
+      errorHandlersCalled++;
+    });
+    worker.addEventListener("error", (_e: Event) => {
+      errorHandlersCalled++;
+      promise2.resolve();
+    });
+
+    worker.postMessage("ping");
+    await promise1;
+    assertEquals(messageHandlersCalled, 3);
+
+    worker.postMessage("boom");
+    await promise2;
+    assertEquals(errorHandlersCalled, 3);
+    worker.terminate();
+  },
+});