4 files changed, 102 insertions, 18 deletions
diff --git a/cli/tests/subdir/busy_worker.js b/cli/tests/subdir/busy_worker.js
new file mode 100644
index 000000000..7deba0321
--- /dev/null
+++ b/cli/tests/subdir/busy_worker.js
@@ -0,0 +1,8 @@
+self.onmessage = function (_evt) {
+  // infinite loop
+  for (let i = 0; true; i++) {
+    if (i % 1000 == 0) {
+      postMessage(i);
+    }
+  }
+};
diff --git a/cli/tests/subdir/racy_worker.js b/cli/tests/subdir/racy_worker.js
new file mode 100644
index 000000000..83756b791
--- /dev/null
+++ b/cli/tests/subdir/racy_worker.js
@@ -0,0 +1,21 @@
+// See issue for details
+// https://github.com/denoland/deno/issues/4080
+//
+// After first call to `postMessage() this worker schedules
+// [close(), postMessage()] ops on the same turn of microtask queue
+// (because message is rather big).
+// Only single `postMessage()` call should make it
+// to host, ie. after calling `close()` no more code should be run.
+
+setTimeout(() => {
+  close();
+}, 50);
+
+while (true) {
+  await new Promise((done) => {
+    setTimeout(() => {
+      postMessage({ buf: new Array(999999) });
+      done();
+    });
+  });
+}
diff --git a/cli/tests/workers_test.out b/cli/tests/workers_test.out
index efc0ce57c..ca7500917 100644
--- a/cli/tests/workers_test.out
+++ b/cli/tests/workers_test.out
@@ -1,7 +1,9 @@
-running 4 tests
-test workersBasic ... ok [WILDCARD]
-test nestedWorker ... ok [WILDCARD]
-test workerThrowsWhenExecuting ... ok [WILDCARD]
-test workerCanUseFetch ... ok [WILDCARD]
+running 6 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 result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out [WILDCARD]
+test result: ok. 6 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 42bd96d96..2c56a491c 100644
--- a/cli/tests/workers_test.ts
+++ b/cli/tests/workers_test.ts
@@ -28,11 +28,10 @@ export function createResolvable<T>(): Resolvable<T> {
 }
 
 Deno.test({
-  name: "workersBasic",
-  // FIXME(bartlomieju):
-  disableOpSanitizer: true,
+  name: "worker terminate",
   fn: async function (): Promise<void> {
     const promise = createResolvable();
+
     const jsWorker = new Worker("../tests/subdir/test_worker.js", {
       type: "module",
       name: "jsWorker",
@@ -59,13 +58,13 @@ Deno.test({
 
     jsWorker.postMessage("Hello World");
     await promise;
+    tsWorker.terminate();
+    jsWorker.terminate();
   },
 });
 
 Deno.test({
-  name: "nestedWorker",
-  // FIXME(bartlomieju):
-  disableOpSanitizer: true,
+  name: "worker nested",
   fn: async function (): Promise<void> {
     const promise = createResolvable();
 
@@ -81,13 +80,12 @@ Deno.test({
 
     nestedWorker.postMessage("Hello World");
     await promise;
+    nestedWorker.terminate();
   },
 });
 
 Deno.test({
-  name: "workerThrowsWhenExecuting",
-  // FIXME(bartlomieju):
-  disableOpSanitizer: true,
+  name: "worker throws when executing",
   fn: async function (): Promise<void> {
     const promise = createResolvable();
     const throwingWorker = new Worker("../tests/subdir/throwing_worker.js", {
@@ -102,13 +100,12 @@ Deno.test({
     };
 
     await promise;
+    throwingWorker.terminate();
   },
 });
 
 Deno.test({
-  name: "workerCanUseFetch",
-  // FIXME(bartlomieju):
-  disableOpSanitizer: true,
+  name: "worker fetch API",
   fn: async function (): Promise<void> {
     const promise = createResolvable();
 
@@ -129,5 +126,61 @@ Deno.test({
     };
 
     await promise;
+    fetchingWorker.terminate();
+  },
+});
+
+Deno.test({
+  name: "worker terminate busy loop",
+  fn: async function (): Promise<void> {
+    const promise = createResolvable();
+
+    const busyWorker = new Worker("../tests/subdir/busy_worker.js", {
+      type: "module",
+    });
+
+    let testResult = 0;
+
+    busyWorker.onmessage = (e): void => {
+      testResult = e.data;
+      if (testResult >= 10000) {
+        busyWorker.terminate();
+        busyWorker.onmessage = (_e): void => {
+          throw new Error("unreachable");
+        };
+        setTimeout(() => {
+          assertEquals(testResult, 10000);
+          promise.resolve();
+        }, 100);
+      }
+    };
+
+    busyWorker.postMessage("ping");
+    await promise;
+  },
+});
+
+Deno.test({
+  name: "worker race condition",
+  fn: async function (): Promise<void> {
+    // See issue for details
+    // https://github.com/denoland/deno/issues/4080
+    const promise = createResolvable();
+
+    const racyWorker = new Worker("../tests/subdir/racy_worker.js", {
+      type: "module",
+    });
+
+    racyWorker.onmessage = (e): void => {
+      assertEquals(e.data.buf.length, 999999);
+      racyWorker.onmessage = (_e): void => {
+        throw new Error("unreachable");
+      };
+      setTimeout(() => {
+        promise.resolve();
+      }, 100);
+    };
+
+    await promise;
   },
 });