chore(workers): Test that closing a worker closes any child workers (#12215)

Before #12156, closing a worker which had children would cause a panic
(https://github.com/denoland/deno/issues/11342#issuecomment-918327693).

After that PR, closing a worker will also close any child workers.

4 files changed, 45 insertions, 0 deletions

diff --git a/cli/tests/testdata/worker_close_nested.js b/cli/tests/testdata/worker_close_nested.js
new file mode 100644
index 000000000..fd47a5ae4
--- /dev/null
+++ b/cli/tests/testdata/worker_close_nested.js
@@ -0,0 +1,20 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+// Test that closing a worker which has living child workers will automatically
+// close the children.
+
+console.log("Starting the main thread");
+
+const worker = new Worker(
+  new URL("./workers/close_nested_parent.js", import.meta.url),
+  { type: "module" },
+);
+
+setTimeout(() => {
+  console.log("About to close");
+  worker.postMessage({});
+
+  // Keep the process running for another two seconds, to make sure there's no
+  // output from the child worker.
+  setTimeout(() => {}, 2000);
+}, 1000);
diff --git a/cli/tests/testdata/worker_close_nested.js.out b/cli/tests/testdata/worker_close_nested.js.out
new file mode 100644
index 000000000..496bc6251
--- /dev/null
+++ b/cli/tests/testdata/worker_close_nested.js.out
@@ -0,0 +1,5 @@
+Starting the main thread
+Starting the parent worker
+Starting the child worker
+About to close
+Closing
diff --git a/cli/tests/testdata/workers/close_nested_child.js b/cli/tests/testdata/workers/close_nested_child.js
new file mode 100644
index 000000000..627a176aa
--- /dev/null
+++ b/cli/tests/testdata/workers/close_nested_child.js
@@ -0,0 +1,7 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+console.log("Starting the child worker");
+
+setTimeout(() => {
+  console.log("The child worker survived the death of the parent!!!");
+}, 2000);
diff --git a/cli/tests/testdata/workers/close_nested_parent.js b/cli/tests/testdata/workers/close_nested_parent.js
new file mode 100644
index 000000000..c528632ce
--- /dev/null
+++ b/cli/tests/testdata/workers/close_nested_parent.js
@@ -0,0 +1,13 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+console.log("Starting the parent worker");
+
+new Worker(
+  new URL("./close_nested_child.js", import.meta.url),
+  { type: "module" },
+);
+
+self.addEventListener("message", () => {
+  console.log("Closing");
+  self.close();
+});