3 files changed, 57 insertions, 2 deletions
diff --git a/cli/tests/subdir/event_worker.js b/cli/tests/subdir/event_worker.js
new file mode 100644
index 000000000..849b6026c
--- /dev/null
+++ b/cli/tests/subdir/event_worker.js
@@ -0,0 +1,7 @@
+onmessage = function (e) {
+  if (e.data === "boom") {
+    throw new Error("boom error!");
+  }
+
+  postMessage(e.data);
+};
diff --git a/cli/tests/workers_test.out b/cli/tests/workers_test.out
index ca7500917..541adc20f 100644
--- a/cli/tests/workers_test.out
+++ b/cli/tests/workers_test.out
@@ -1,9 +1,10 @@
-running 6 tests
+running 7 tests
 test worker terminate ... ok [WILDCARD]
 test worker nested ... ok [WILDCARD]
 test worker throws when executing ... ok [WILDCARD]
 test worker fetch API ... ok [WILDCARD]
 test worker terminate busy loop ... ok [WILDCARD]
 test worker race condition ... ok [WILDCARD]
+test worker is event listener ... ok [WILDCARD]
 
-test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out [WILDCARD]
+test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out [WILDCARD]
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();
+  },
+});