bun:test: bound expect() promise waits by the test timeout

src/runtime/test_runner/expect.rs

@@ -471,6 +471,36 @@
         }
     }
 
+    /// `wait_for_promise` bounded by the test's deadline; returns `true` if still pending.
+    fn wait_for_promise_bounded_by_test(
+        global_this: &JSGlobalObject,
+        promise: bun_jsc::AnyPromise,
+    ) -> bool {
+        use bun_core::{Timespec, TimespecMockMode};
+        if promise.status() != js_promise::Status::Pending {
+            return false;
+        }
+        let deadline = Jest::runner().map_or(Timespec::EPOCH, |r| r.get_active_timeout());
+        let jsc_vm = global_this.vm();
+        let bun_vm = global_this.bun_vm().as_mut();
+        while promise.status() == js_promise::Status::Pending {
+            if jsc_vm.execution_forbidden() {
+                break;
+            }
+            if !deadline.eql(&Timespec::EPOCH)
+                && deadline.order(&Timespec::now(TimespecMockMode::ForceRealTime))
+                    == core::cmp::Ordering::Less
+            {
+                break;
+            }
+            bun_vm.event_loop_mut().tick();
+            if promise.status() == js_promise::Status::Pending {
+                bun_vm.event_loop_mut().auto_tick();
+            }
+        }
+        promise.status() == js_promise::Status::Pending
+    }
+
     /// Processes the async flags (resolves/rejects), waiting for the async value if needed.
     /// If no flags, returns the original value
     /// If either flag is set, waits for the result, and returns either it as a JSValue, or null if the expectation failed (in which case if silent is false, also throws a js exception)
@@ -489,8 +519,17 @@
                     let vm = global_this.vm();
                     promise.set_handled(vm);
 
-                    // SAFETY: bun_vm() returns the live thread-local VirtualMachine.
-            global_this.bun_vm().as_mut().wait_for_promise(promise);
+                    if Self::wait_for_promise_bounded_by_test(global_this, promise) {
+                        if !silent {
+                            return Err(Self::throw_promise_matcher_error(
+                                global_this, custom_label, matcher_name, matcher_params, flags,
+                                "Expected promise to settle within the test timeout",
+                                "Received promise that is still pending: ",
+                                "[Promise]",
+                            ));
+                        }
+                        return Err(JsError::Thrown);
+                    }
 
                     let new_value = promise.result(vm);
                     match promise.status() {
@@ -892,9 +931,14 @@
             return_value = return_value_from_function;
         }
 
         if let Some(promise) = return_value.as_any_promise() {
-            vm.wait_for_promise(promise);
+            let still_pending = Self::wait_for_promise_bounded_by_test(global_this, promise);
             scope.apply(vm);
+            if still_pending {
+                return Err(global_this.throw(format_args!(
+                    "Received function returned a promise that did not settle within the test timeout",
+                )));
+            }
             match promise.unwrap(global_this.vm(), js_promise::UnwrapMode::MarkHandled) {
                 js_promise::Unwrapped::Fulfilled(_) => {
                     return Ok((None, return_value_from_function));
@@ -1487,8 +1531,12 @@
             let vm = global_this.vm();
             promise.set_handled(vm);
 
-            // SAFETY: bun_vm() returns the live thread-local VirtualMachine.
-            global_this.bun_vm().as_mut().wait_for_promise(promise);
+            if Self::wait_for_promise_bounded_by_test(global_this, promise) {
+                return Err(global_this.throw(format_args!(
+                    "Matcher `{}` returned a promise that did not settle within the test timeout",
+                    matcher_name,
+                )));
+            }
 
             result = promise.result(vm);
             result.ensure_still_alive();

test/regression/issue/14950.test.ts

@@ -0,0 +1,117 @@
+// https://github.com/oven-sh/bun/issues/14950
+// `expect(pendingPromise).resolves.<matcher>()` in a sync test body must not
+// hang `bun test` forever at 100% CPU; the per-test timeout has to fire.
+import { describe, expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir } from "harness";
+
+async function runTestFile(name: string, body: string) {
+  using dir = tempDir(name, { "t.test.js": body });
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "test", "t.test.js", "--timeout", "500"],
+    env: bunEnv,
+    cwd: String(dir),
+    stderr: "pipe",
+    stdout: "pipe",
+  });
+  // On an unfixed build the inner runner never exits (the per-test --timeout
+  // cannot interrupt the wait_for_promise spin), so kill it ourselves instead
+  // of letting the outer runner's own timeout abort the assertion.
+  let hung = false;
+  const watchdog = setTimeout(() => {
+    hung = true;
+    proc.kill();
+  }, 20_000);
+  try {
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+    return { stdout, stderr, exitCode, hung };
+  } finally {
+    clearTimeout(watchdog);
+  }
+}
+
+describe.concurrent("expect().resolves/.rejects on a not-yet-settled promise", () => {
+  test(".resolves on a promise resolved after the matcher call times out instead of hanging", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-resolves",
+      `test("promise resolves after expect call", () => {
+           let resolve;
+           expect(new Promise(r => (resolve = r))).resolves.toBe(25);
+           resolve(25);
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toContain("still pending");
+    expect(stderr).toMatch(/timed out after \d+ms/);
+    expect(exitCode).toBe(1);
+  }, 60_000);
+
+  test(".rejects on a never-settling promise times out instead of hanging", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-rejects",
+      `test("never settles", () => {
+           expect(new Promise(() => {})).rejects.toThrow();
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toContain("still pending");
+    expect(stderr).toMatch(/timed out after \d+ms/);
+    expect(exitCode).toBe(1);
+  }, 60_000);
+
+  test("toThrow on an async fn returning a never-settling promise times out instead of hanging", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-tothrow",
+      `test("never settles", () => {
+           expect(() => new Promise(() => {})).toThrow();
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toContain("did not settle within the test timeout");
+    expect(exitCode).toBe(1);
+  }, 60_000);
+
+  test("async custom matcher returning a never-settling promise times out instead of hanging", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-custom",
+      `const { expect, test } = require("bun:test");
+         expect.extend({
+           toNeverSettle() { return new Promise(() => {}); },
+         });
+         test("never settles", () => {
+           expect(1).toNeverSettle();
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toContain("did not settle within the test timeout");
+    expect(exitCode).toBe(1);
+  }, 60_000);
+
+  test("a test after one that spins on .resolves still runs", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-next-test",
+      `test("hangs", () => {
+           expect(new Promise(() => {})).resolves.toBe(1);
+         });
+         test("runs after", () => {
+           expect(1).toBe(1);
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toMatch(/1 pass/);
+    expect(stderr).toMatch(/1 fail/);
+    expect(exitCode).toBe(1);
+  }, 60_000);
+
+  test(".resolves on an already-resolved promise still passes synchronously", async () => {
+    const { stderr, exitCode, hung } = await runTestFile(
+      "issue-14950-settled",
+      `test("already settled", () => {
+           expect(Promise.resolve(25)).resolves.toBe(25);
+         });`,
+    );
+    expect(hung).toBe(false);
+    expect(stderr).toMatch(/1 pass/);
+    expect(stderr).not.toContain("still pending");
+    expect(exitCode).toBe(0);
+  }, 60_000);
+});

test/regression/issue/23865.test.ts

@@ -16,6 +16,15 @@ test("23865", async () => {
   expect(normalizeBunSnapshot(stdout)).toMatchInlineSnapshot(`"bun test <version> (<revision>)"`);
   expect(normalizeBunSnapshot(stderr)).toMatchInlineSnapshot(`
     "23865.fixture.ts:
+    1 | // Should not crash
+    2 | test("abc", () => {
+    3 |   expect(async () => {
+    4 |     await Bun.sleep(100);
+    5 |     throw new Error("uh oh!");
+    6 |   }).toThrow("uh oh!");
+             ^
+    error: Received function returned a promise that did not settle within the test timeout
+        at <anonymous> (file:NN:NN)
     (fail) abc
       ^ this test timed out after 50ms.