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Speed up shell leak test - #25880

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jarred/speed-up-shell-leak-test
Jan 8, 2026
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Jarred-Sumner merged 2 commits into
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jarred/speed-up-shell-leak-test

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What does this PR do?

18s -> 3s

How did you verify your code works?

@robobun

robobun commented Jan 8, 2026 •

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Updated 9:32 PM PT - Jan 7th, 2026

❌ @Jarred-Sumner, your commit e48f099 has 5 failures in Build #34218 (All Failures):


🧪   To try this PR locally:

bunx bun-pr 25880

That installs a local version of the PR into your bun-25880 executable, so you can run:

bun-25880 --bun

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Walkthrough

Refactors shell leak tests to run asynchronously with Bun.spawn, converts main suite to concurrent execution while keeping some suites serial, and removes TestBuilder's runtime test-scope enforcement and its associated hooks.

Changes

Cohort / File(s) Summary
Shell leak test suite
test/js/bun/shell/leak.test.ts
Replaced synchronous Bun.spawnSync runs with async Bun.spawn, piping stderr and awaiting exit via exited/text(); changed main describe to describe.concurrent, made specific containers (#11816, leak-not-leaking/ParsedShellScript) describe.serial; log captured stderr on failures.
Test builder scope enforcement removal
test/js/bun/shell/test_builder.ts
Removed global insideTestScope tracking, its beforeEach/afterEach hooks, and the runtime guard in TestBuilder.run() that enforced invocation inside a test scope.

Possibly related PRs

Suggested reviewers

  • cirospaciari
🚥 Pre-merge checks | ✅ 1 | ❌ 1
❌ Failed checks (1 inconclusive)
Check name Status Explanation Resolution
Description check ❓ Inconclusive The description is minimally completed with only brief performance metrics (18s -> 3s) but lacks substantive details about implementation approach and verification. Expand the description to explain the key optimization approach (e.g., concurrent vs. serial execution, script generation) and provide more detailed verification steps beyond the performance claim.
✅ Passed checks (1 passed)
Check name Status Explanation
Title check ✅ Passed The title 'Speed up shell leak test' is specific and directly describes the main objective of the changeset—optimizing the performance of a shell leak test.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.


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Actionable comments posted: 1

🤖 Fix all issues with AI agents
In @test/js/bun/shell/leak.test.ts:
- Line 381: Remove the unnecessary async from the describe.serial callback for
"#11816" (i.e., change describe.serial("#11816", async () => { ... }) to
describe.serial("#11816", () => { ... })), since the callback contains no await
and the async keyword is redundant.
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📥 Commits

Reviewing files that changed from the base of the PR and between ff590e9 and 8a803ef.

📒 Files selected for processing (2)
  • test/js/bun/shell/leak.test.ts
  • test/js/bun/shell/test_builder.ts
💤 Files with no reviewable changes (1)
  • test/js/bun/shell/test_builder.ts
🧰 Additional context used
📓 Path-based instructions (3)
**/*.test.ts?(x)

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.test.ts?(x): Never use bun test directly - always use bun bd test to run tests with debug build changes
For single-file tests, prefer -e flag over tempDir
For multi-file tests, prefer tempDir and Bun.spawn over single-file tests
Use normalizeBunSnapshot to normalize snapshot output of tests
Never write tests that check for 'panic', 'uncaught exception', or similar strings in test output
Use tempDir from harness to create temporary directories - do not use tmpdirSync or fs.mkdtempSync
When spawning processes in tests, expect stdout before expecting exit code for more useful error messages on test failure
Do not write flaky tests - do not use setTimeout in tests; instead await the condition to be met
Verify tests fail with USE_SYSTEM_BUN=1 bun test <file> and pass with bun bd test <file> - tests are invalid if they pass with USE_SYSTEM_BUN=1
Test files must end with .test.ts or .test.tsx
Avoid shell commands like find or grep in tests - use Bun's Glob and built-in tools instead

Files:

  • test/js/bun/shell/leak.test.ts
test/**/*.test.ts?(x)

📄 CodeRabbit inference engine (CLAUDE.md)

Always use port: 0 in tests - do not hardcode ports or use custom random port number functions

Files:

  • test/js/bun/shell/leak.test.ts
test/**/*.test.{ts,js,jsx,tsx,mjs,cjs}

📄 CodeRabbit inference engine (test/CLAUDE.md)

test/**/*.test.{ts,js,jsx,tsx,mjs,cjs}: Use bun bd test <...test file> to run tests with compiled code changes. Do not use bun test as it will not include your changes.
Use bun:test for files ending in *.test.{ts,js,jsx,tsx,mjs,cjs}. For test files without .test extension in test/js/node/test/{parallel,sequential}/*.js, use bun bd <file> instead of bun bd test <file> since they expect exit code 0.
Do not set a timeout on tests. Bun already has timeouts built-in.

Files:

  • test/js/bun/shell/leak.test.ts
🧠 Learnings (22)
📓 Common learnings
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer concurrent tests over sequential tests. Use `test.concurrent` or `describe.concurrent` when multiple tests spawn processes or write files, unless it is very difficult to make them concurrent.
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 24417
File: test/js/bun/spawn/spawn.test.ts:903-918
Timestamp: 2025-11-06T00:58:23.965Z
Learning: In Bun test files, `await using` with spawn() is appropriate for long-running processes that need guaranteed cleanup on scope exit or when explicitly testing disposal behavior. For short-lived processes that exit naturally (e.g., console.log scripts), the pattern `const proc = spawn(...); await proc.exited;` is standard and more common, as evidenced by 24 instances vs 4 `await using` instances in test/js/bun/spawn/spawn.test.ts.
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : When spawning processes in tests, expect stdout before expecting exit code for more useful error messages on test failure

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-26T01:32:04.844Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24082
File: test/cli/test/coverage.test.ts:60-112
Timestamp: 2025-10-26T01:32:04.844Z
Learning: In the Bun repository test files (test/cli/test/*.test.ts), when spawning Bun CLI commands with Bun.spawnSync for testing, prefer using stdio: ["inherit", "inherit", "inherit"] to inherit stdio streams rather than piping them.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : For multi-file tests, prefer `tempDir` and `Bun.spawn` over single-file tests

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-06T00:58:23.965Z
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 24417
File: test/js/bun/spawn/spawn.test.ts:903-918
Timestamp: 2025-11-06T00:58:23.965Z
Learning: In Bun test files, `await using` with spawn() is appropriate for long-running processes that need guaranteed cleanup on scope exit or when explicitly testing disposal behavior. For short-lived processes that exit naturally (e.g., console.log scripts), the pattern `const proc = spawn(...); await proc.exited;` is standard and more common, as evidenced by 24 instances vs 4 `await using` instances in test/js/bun/spawn/spawn.test.ts.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-24T18:36:59.706Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: src/bun.js/bindings/v8/CLAUDE.md:0-0
Timestamp: 2025-11-24T18:36:59.706Z
Learning: Applies to src/bun.js/bindings/v8/test/v8/v8.test.ts : Add corresponding test cases to test/v8/v8.test.ts using checkSameOutput() function to compare Node.js and Bun output

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer concurrent tests over sequential tests. Use `test.concurrent` or `describe.concurrent` when multiple tests spawn processes or write files, unless it is very difficult to make them concurrent.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Avoid shell commands like `find` or `grep` in tests - use Bun's Glob and built-in tools instead

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-08T04:06:33.198Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24491
File: test/js/bun/transpiler/declare-global.test.ts:17-17
Timestamp: 2025-11-08T04:06:33.198Z
Learning: In Bun test files, `await using` with Bun.spawn() is the preferred pattern for spawned processes regardless of whether they are short-lived or long-running. Do not suggest replacing `await using proc = Bun.spawn(...)` with `const proc = Bun.spawn(...); await proc.exited;`.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun bd test <...test file>` to run tests with compiled code changes. Do not use `bun test` as it will not include your changes.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to test/**/*.test.ts?(x) : Always use `port: 0` in tests - do not hardcode ports or use custom random port number functions

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-09-20T03:39:41.770Z
Learnt from: pfgithub
Repo: oven-sh/bun PR: 22534
File: test/regression/issue/21830.fixture.ts:14-63
Timestamp: 2025-09-20T03:39:41.770Z
Learning: Bun's test runner supports async describe callbacks, unlike Jest/Vitest where describe callbacks must be synchronous. The syntax `describe("name", async () => { ... })` is valid in Bun.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-30T03:48:10.513Z
Learnt from: theshadow27
Repo: oven-sh/bun PR: 24063
File: packages/bun-otel/test/context-propagation.test.ts:1-7
Timestamp: 2025-10-30T03:48:10.513Z
Learning: In Bun test files, `using` declarations at the describe block level execute during module load/parsing, not during test execution. This means they acquire and dispose resources before any tests run. For test-scoped resource management, use beforeAll/afterAll hooks instead. The pattern `beforeAll(beforeUsingEchoServer); afterAll(afterUsingEchoServer);` is correct for managing ref-counted test resources like the EchoServer in packages/bun-otel/test/ - the using block pattern should not be used at describe-block level for test resources.
<!-- [/add_learning]

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Do not write flaky tests - do not use `setTimeout` in tests; instead await the condition to be met

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-08T13:48:02.430Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 23373
File: test/js/bun/tarball/extract.test.ts:107-111
Timestamp: 2025-10-08T13:48:02.430Z
Learning: In Bun's test runner, use `expect(async () => { await ... }).toThrow()` to assert async rejections. Unlike Jest/Vitest, Bun does not require `await expect(...).rejects.toThrow()` - the async function wrapper with `.toThrow()` is the correct pattern for async error assertions in Bun tests.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun:test` for files ending in `*.test.{ts,js,jsx,tsx,mjs,cjs}`. For test files without .test extension in test/js/node/test/{parallel,sequential}/*.js, use `bun bd <file>` instead of `bun bd test <file>` since they expect exit code 0.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Always check exit codes and test error scenarios when spawning processes in tests.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Use `-e` flag for single-file tests when spawning Bun processes with `Bun.spawn()`.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Verify tests fail with `USE_SYSTEM_BUN=1 bun test <file>` and pass with `bun bd test <file>` - tests are invalid if they pass with USE_SYSTEM_BUN=1

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : For single-file tests, prefer `-e` flag over `tempDir`

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Never use `bun test` directly - always use `bun bd test` to run tests with debug build changes

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Never write tests that check for 'panic', 'uncaught exception', or similar strings in test output

Applied to files:

  • test/js/bun/shell/leak.test.ts
🧬 Code graph analysis (1)
test/js/bun/shell/leak.test.ts (1)
test/js/bun/shell/bunshell.test.ts (1)
  • bunEnv (18-31)
🔇 Additional comments (4)
test/js/bun/shell/leak.test.ts (4)

56-56: Good use of describe.concurrent for parallel test execution.

This change aligns with the coding guidelines to prefer concurrent tests when multiple tests spawn processes. The parallelization should deliver the claimed 6x speedup. Based on learnings.


126-136: Async spawn pattern looks correct.

The pattern of piping stderr, awaiting both exited and stream.text() via Promise.all, and logging stderr on failure provides good debugging output when tests fail.


220-230: Consistent async spawn pattern with appropriate stdout handling.

Ignoring stdout with stdout: "ignore" is appropriate here since the test only needs stderr for diagnostics. The pattern is consistent with the other spawn usage in this file.


414-451: Correct use of describe.serial for order-dependent tests.

Using describe.serial within the concurrent parent is the right pattern here. These tests manipulate GC and check heap object counts, where running them in parallel could cause interference. The tests can still benefit from the outer concurrent execution while maintaining correctness.

);

describe("#11816", async () => {
describe.serial("#11816", async () => {

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🧹 Nitpick | 🔵 Trivial

Unnecessary async keyword on describe callback.

The async on this describe callback is unnecessary since there's no await in the callback body. Line 414 correctly omits it.

Suggested fix
-  describe.serial("#11816", async () => {
+  describe.serial("#11816", () => {
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
describe.serial("#11816", async () => {
describe.serial("#11816", () => {
🤖 Prompt for AI Agents
In @test/js/bun/shell/leak.test.ts at line 381, Remove the unnecessary async
from the describe.serial callback for "#11816" (i.e., change
describe.serial("#11816", async () => { ... }) to describe.serial("#11816", ()
=> { ... })), since the callback contains no await and the async keyword is
redundant.

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Actionable comments posted: 2

🤖 Fix all issues with AI agents
In @test/js/bun/shell/leak.test.ts:
- Line 235: Replace the direct use of process.argv0 with the helper bunExe() to
keep spawn invocation consistent; in the Bun.spawn call that destructures {
stderr: stream, exited } and currently passes [process.argv0, "--smol", "test",
join(dir, "script.ts")], swap process.argv0 for bunExe() so the array becomes
[bunExe(), "--smol", "test", join(dir, "script.ts")] to match the other tests
using bunExe().
- Line 89: Replace usage of process.argv0 in the Bun.spawn call with the
project's helper bunExe() for consistency; update the spawn invocation that
currently passes process.argv0 (inside the test invoking Bun.spawn with
["process.argv0", "--smol", "test", join(dir, "script.ts")]) to call bunExe()
instead so it matches other tests that use bunExe() (see other occurrences
around bunExe() at lines 371 and 408) and preserves existing arguments and
options.
📜 Review details

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Review profile: ASSERTIVE

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📥 Commits

Reviewing files that changed from the base of the PR and between 8a803ef and e48f099.

📒 Files selected for processing (1)
  • test/js/bun/shell/leak.test.ts
🧰 Additional context used
📓 Path-based instructions (3)
**/*.test.ts?(x)

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.test.ts?(x): Never use bun test directly - always use bun bd test to run tests with debug build changes
For single-file tests, prefer -e flag over tempDir
For multi-file tests, prefer tempDir and Bun.spawn over single-file tests
Use normalizeBunSnapshot to normalize snapshot output of tests
Never write tests that check for 'panic', 'uncaught exception', or similar strings in test output
Use tempDir from harness to create temporary directories - do not use tmpdirSync or fs.mkdtempSync
When spawning processes in tests, expect stdout before expecting exit code for more useful error messages on test failure
Do not write flaky tests - do not use setTimeout in tests; instead await the condition to be met
Verify tests fail with USE_SYSTEM_BUN=1 bun test <file> and pass with bun bd test <file> - tests are invalid if they pass with USE_SYSTEM_BUN=1
Test files must end with .test.ts or .test.tsx
Avoid shell commands like find or grep in tests - use Bun's Glob and built-in tools instead

Files:

  • test/js/bun/shell/leak.test.ts
test/**/*.test.ts?(x)

📄 CodeRabbit inference engine (CLAUDE.md)

Always use port: 0 in tests - do not hardcode ports or use custom random port number functions

Files:

  • test/js/bun/shell/leak.test.ts
test/**/*.test.{ts,js,jsx,tsx,mjs,cjs}

📄 CodeRabbit inference engine (test/CLAUDE.md)

test/**/*.test.{ts,js,jsx,tsx,mjs,cjs}: Use bun bd test <...test file> to run tests with compiled code changes. Do not use bun test as it will not include your changes.
Use bun:test for files ending in *.test.{ts,js,jsx,tsx,mjs,cjs}. For test files without .test extension in test/js/node/test/{parallel,sequential}/*.js, use bun bd <file> instead of bun bd test <file> since they expect exit code 0.
Do not set a timeout on tests. Bun already has timeouts built-in.

Files:

  • test/js/bun/shell/leak.test.ts
🧠 Learnings (30)
📓 Common learnings
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Do not set a timeout on tests. Bun already has timeouts built-in.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer concurrent tests over sequential tests. Use `test.concurrent` or `describe.concurrent` when multiple tests spawn processes or write files, unless it is very difficult to make them concurrent.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: When spawning Bun processes in tests, use `bunExe` and `bunEnv` from `harness` to ensure the same build of Bun is used and debug logging is silenced.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : For multi-file tests, prefer `tempDir` and `Bun.spawn` over single-file tests
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Use `-e` flag for single-file tests when spawning Bun processes with `Bun.spawn()`.
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24491
File: test/js/bun/transpiler/declare-global.test.ts:17-17
Timestamp: 2025-11-08T04:06:33.198Z
Learning: In Bun test files, `await using` with Bun.spawn() is the preferred pattern for spawned processes regardless of whether they are short-lived or long-running. Do not suggest replacing `await using proc = Bun.spawn(...)` with `const proc = Bun.spawn(...); await proc.exited;`.
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 24417
File: test/js/bun/spawn/spawn.test.ts:903-918
Timestamp: 2025-11-06T00:58:23.965Z
Learning: In Bun test files, `await using` with spawn() is appropriate for long-running processes that need guaranteed cleanup on scope exit or when explicitly testing disposal behavior. For short-lived processes that exit naturally (e.g., console.log scripts), the pattern `const proc = spawn(...); await proc.exited;` is standard and more common, as evidenced by 24 instances vs 4 `await using` instances in test/js/bun/spawn/spawn.test.ts.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun bd test <...test file>` to run tests with compiled code changes. Do not use `bun test` as it will not include your changes.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun:test` for files ending in `*.test.{ts,js,jsx,tsx,mjs,cjs}`. For test files without .test extension in test/js/node/test/{parallel,sequential}/*.js, use `bun bd <file>` instead of `bun bd test <file>` since they expect exit code 0.
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24082
File: test/cli/test/coverage.test.ts:60-112
Timestamp: 2025-10-26T01:32:04.844Z
Learning: In the Bun repository test files (test/cli/test/*.test.ts), when spawning Bun CLI commands with Bun.spawnSync for testing, prefer using stdio: ["inherit", "inherit", "inherit"] to inherit stdio streams rather than piping them.
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun bd test <...test file>` to run tests with compiled code changes. Do not use `bun test` as it will not include your changes.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-24T18:36:59.706Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: src/bun.js/bindings/v8/CLAUDE.md:0-0
Timestamp: 2025-11-24T18:36:59.706Z
Learning: Applies to src/bun.js/bindings/v8/test/v8/v8.test.ts : Add corresponding test cases to test/v8/v8.test.ts using checkSameOutput() function to compare Node.js and Bun output

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : For multi-file tests, prefer `tempDir` and `Bun.spawn` over single-file tests

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-26T01:32:04.844Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24082
File: test/cli/test/coverage.test.ts:60-112
Timestamp: 2025-10-26T01:32:04.844Z
Learning: In the Bun repository test files (test/cli/test/*.test.ts), when spawning Bun CLI commands with Bun.spawnSync for testing, prefer using stdio: ["inherit", "inherit", "inherit"] to inherit stdio streams rather than piping them.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Never use `bun test` directly - always use `bun bd test` to run tests with debug build changes

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Use `bun:test` for files ending in `*.test.{ts,js,jsx,tsx,mjs,cjs}`. For test files without .test extension in test/js/node/test/{parallel,sequential}/*.js, use `bun bd <file>` instead of `bun bd test <file>` since they expect exit code 0.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-06T00:58:23.965Z
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 24417
File: test/js/bun/spawn/spawn.test.ts:903-918
Timestamp: 2025-11-06T00:58:23.965Z
Learning: In Bun test files, `await using` with spawn() is appropriate for long-running processes that need guaranteed cleanup on scope exit or when explicitly testing disposal behavior. For short-lived processes that exit naturally (e.g., console.log scripts), the pattern `const proc = spawn(...); await proc.exited;` is standard and more common, as evidenced by 24 instances vs 4 `await using` instances in test/js/bun/spawn/spawn.test.ts.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Avoid shell commands like `find` or `grep` in tests - use Bun's Glob and built-in tools instead

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : When spawning processes in tests, expect stdout before expecting exit code for more useful error messages on test failure

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-19T04:55:33.099Z
Learnt from: theshadow27
Repo: oven-sh/bun PR: 23798
File: test/js/bun/http/node-telemetry.test.ts:27-203
Timestamp: 2025-10-19T04:55:33.099Z
Learning: In test/js/bun/http/node-telemetry.test.ts and the Bun.telemetry._node_binding API, after the architecture refactor, the _node_binding interface only contains two methods: handleIncomingRequest(req, res) and handleWriteHead(res, statusCode). The handleRequestFinish hook and other lifecycle hooks were removed during simplification. Both current methods are fully tested.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-09-20T03:39:41.770Z
Learnt from: pfgithub
Repo: oven-sh/bun PR: 22534
File: test/regression/issue/21830.fixture.ts:14-63
Timestamp: 2025-09-20T03:39:41.770Z
Learning: Bun's test runner supports async describe callbacks, unlike Jest/Vitest where describe callbacks must be synchronous. The syntax `describe("name", async () => { ... })` is valid in Bun.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-09-20T00:57:56.685Z
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 22568
File: test/js/valkey/valkey.test.ts:268-276
Timestamp: 2025-09-20T00:57:56.685Z
Learning: For test/js/valkey/valkey.test.ts, do not comment on synchronous throw assertions for async Redis methods like ctx.redis.set() - the maintainer has explicitly requested to stop looking at this error pattern.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-09-20T00:58:38.042Z
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 22568
File: test/js/valkey/valkey.test.ts:561-564
Timestamp: 2025-09-20T00:58:38.042Z
Learning: For test/js/valkey/valkey.test.ts, do not comment on synchronous throw assertions for async Redis methods (like ctx.redis.set(), ctx.redis.unsubscribe(), etc.) - Bun's Redis client implementation differs from Node.js and can throw synchronously even for async methods. The maintainer has explicitly requested to stop looking at this error pattern.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Do not write flaky tests - do not use `setTimeout` in tests; instead await the condition to be met

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer async/await over callbacks in tests. When callbacks must be used for a single callback, use `Promise.withResolvers` to create a promise that can be resolved or rejected from a callback.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-09-03T01:30:58.001Z
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 21728
File: test/js/valkey/valkey.test.ts:264-271
Timestamp: 2025-09-03T01:30:58.001Z
Learning: For test/js/valkey/valkey.test.ts PUB/SUB tests, avoid arbitrary sleeps and async-forEach. Instead, resolve a Promise from the subscriber callback when the expected number of messages is observed and await it with a bounded timeout (e.g., withTimeout + Promise.withResolvers) to account for Redis server→subscriber propagation.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-08T04:06:33.198Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 24491
File: test/js/bun/transpiler/declare-global.test.ts:17-17
Timestamp: 2025-11-08T04:06:33.198Z
Learning: In Bun test files, `await using` with Bun.spawn() is the preferred pattern for spawned processes regardless of whether they are short-lived or long-running. Do not suggest replacing `await using proc = Bun.spawn(...)` with `const proc = Bun.spawn(...); await proc.exited;`.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-08T13:48:02.430Z
Learnt from: Jarred-Sumner
Repo: oven-sh/bun PR: 23373
File: test/js/bun/tarball/extract.test.ts:107-111
Timestamp: 2025-10-08T13:48:02.430Z
Learning: In Bun's test runner, use `expect(async () => { await ... }).toThrow()` to assert async rejections. Unlike Jest/Vitest, Bun does not require `await expect(...).rejects.toThrow()` - the async function wrapper with `.toThrow()` is the correct pattern for async error assertions in Bun tests.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-11-24T18:37:11.466Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: src/js/CLAUDE.md:0-0
Timestamp: 2025-11-24T18:37:11.466Z
Learning: Write JS builtins for Bun's Node.js compatibility and APIs, and run `bun bd` after changes

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-19T02:44:46.354Z
Learnt from: theshadow27
Repo: oven-sh/bun PR: 23798
File: packages/bun-otel/context-propagation.test.ts:1-1
Timestamp: 2025-10-19T02:44:46.354Z
Learning: In the Bun repository, standalone packages under packages/ (e.g., bun-vscode, bun-inspector-protocol, bun-plugin-yaml, bun-plugin-svelte, bun-debug-adapter-protocol, bun-otel) co-locate their tests with package source code using *.test.ts files. This follows standard npm/monorepo patterns. The test/ directory hierarchy (test/js/bun/, test/cli/, test/js/node/) is reserved for testing Bun's core runtime APIs and built-in functionality, not standalone packages.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: When spawning Bun processes in tests, use `bunExe` and `bunEnv` from `harness` to ensure the same build of Bun is used and debug logging is silenced.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Organize unit tests by module in directories like `/test/js/bun/` and `/test/js/node/`.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Verify tests fail with `USE_SYSTEM_BUN=1 bun test <file>` and pass with `bun bd test <file>` - tests are invalid if they pass with USE_SYSTEM_BUN=1

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer concurrent tests over sequential tests. Use `test.concurrent` or `describe.concurrent` when multiple tests spawn processes or write files, unless it is very difficult to make them concurrent.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-10-30T03:48:10.513Z
Learnt from: theshadow27
Repo: oven-sh/bun PR: 24063
File: packages/bun-otel/test/context-propagation.test.ts:1-7
Timestamp: 2025-10-30T03:48:10.513Z
Learning: In Bun test files, `using` declarations at the describe block level execute during module load/parsing, not during test execution. This means they acquire and dispose resources before any tests run. For test-scoped resource management, use beforeAll/afterAll hooks instead. The pattern `beforeAll(beforeUsingEchoServer); afterAll(afterUsingEchoServer);` is correct for managing ref-counted test resources like the EchoServer in packages/bun-otel/test/ - the using block pattern should not be used at describe-block level for test resources.
<!-- [/add_learning]

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : For single-file tests, prefer `-e` flag over `tempDir`

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Use `tempDir` from `harness` to create temporary directories - do not use `tmpdirSync` or `fs.mkdtempSync`

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2026-01-05T23:04:01.518Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Applies to test/**/*.test.{ts,js,jsx,tsx,mjs,cjs} : Do not set a timeout on tests. Bun already has timeouts built-in.

Applied to files:

  • test/js/bun/shell/leak.test.ts
📚 Learning: 2025-12-16T00:21:32.179Z
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Never write tests that check for 'panic', 'uncaught exception', or similar strings in test output

Applied to files:

  • test/js/bun/shell/leak.test.ts
🧬 Code graph analysis (1)
test/js/bun/shell/leak.test.ts (2)
test/harness.ts (1)
  • tempDir (277-284)
test/js/bun/shell/bunshell.test.ts (1)
  • bunEnv (18-31)
🔇 Additional comments (5)
test/js/bun/shell/leak.test.ts (5)

1-16: LGTM! Imports and setup follow best practices.

The updated imports correctly use tempDir and tempDirWithFiles from harness, and the environment setup with bunEnv is appropriate for test isolation.


54-54: Good use of concurrent and serial test execution.

The refactoring appropriately uses describe.concurrent for the main test suite (line 54) to enable parallel execution, while using describe.serial for tests that require sequential execution (lines 395, 428). This should significantly improve test performance.

Also applies to: 395-395, 428-428


85-87: Excellent resource management with using and tempDir.

The tests correctly use the using keyword with tempDir for automatic cleanup of temporary directories. This follows best practices and ensures resources are properly disposed of even if tests fail.

Based on learnings, using tempDir from harness is the recommended approach for creating temporary directories in tests.

Also applies to: 143-145, 231-233


93-97: Proper error handling and debugging support.

The tests correctly await both the exit code and stderr output in parallel, and log stderr when tests fail. This provides good debugging information when leak tests fail.

Also applies to: 151-156, 240-244


395-395: Unnecessary async keyword on describe callback.

The async keyword on this describe callback is unnecessary since there's no await in the callback body. This was previously flagged in an earlier review.

⛔ Skipped due to learnings
Learnt from: pfgithub
Repo: oven-sh/bun PR: 22534
File: test/regression/issue/21830.fixture.ts:14-63
Timestamp: 2025-09-20T03:39:41.770Z
Learning: Bun's test runner supports async describe callbacks, unlike Jest/Vitest where describe callbacks must be synchronous. The syntax `describe("name", async () => { ... })` is valid in Bun.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: test/CLAUDE.md:0-0
Timestamp: 2026-01-05T23:04:01.518Z
Learning: Prefer async/await over callbacks in tests. When callbacks must be used for a single callback, use `Promise.withResolvers` to create a promise that can be resolved or rejected from a callback.
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 22568
File: test/js/valkey/valkey.test.ts:268-276
Timestamp: 2025-09-20T00:57:56.685Z
Learning: For test/js/valkey/valkey.test.ts, do not comment on synchronous throw assertions for async Redis methods like ctx.redis.set() - the maintainer has explicitly requested to stop looking at this error pattern.
Learnt from: markovejnovic
Repo: oven-sh/bun PR: 22568
File: test/js/valkey/valkey.test.ts:561-564
Timestamp: 2025-09-20T00:58:38.042Z
Learning: For test/js/valkey/valkey.test.ts, do not comment on synchronous throw assertions for async Redis methods (like ctx.redis.set(), ctx.redis.unsubscribe(), etc.) - Bun's Redis client implementation differs from Node.js and can throw synchronously even for async methods. The maintainer has explicitly requested to stop looking at this error pattern.
Learnt from: CR
Repo: oven-sh/bun PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-12-16T00:21:32.179Z
Learning: Applies to **/*.test.ts?(x) : Do not write flaky tests - do not use `setTimeout` in tests; instead await the condition to be met

"script.ts": testcode + impl,
});

const { exited, stderr: stream } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {

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🧹 Nitpick | 🔵 Trivial

Consider using bunExe() for consistency.

Line 89 uses process.argv0 to reference the Bun executable, while other parts of this file use bunExe() (e.g., lines 371, 408). For consistency and clarity, consider using bunExe() throughout.

Suggested change
-      const { exited, stderr: stream } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {
+      const { exited, stderr: stream } = Bun.spawn([bunExe(), "--smol", "test", join(dir, "script.ts")], {
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
const { exited, stderr: stream } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {
const { exited, stderr: stream } = Bun.spawn([bunExe(), "--smol", "test", join(dir, "script.ts")], {
🤖 Prompt for AI Agents
In @test/js/bun/shell/leak.test.ts at line 89, Replace usage of process.argv0 in
the Bun.spawn call with the project's helper bunExe() for consistency; update
the spawn invocation that currently passes process.argv0 (inside the test
invoking Bun.spawn with ["process.argv0", "--smol", "test", join(dir,
"script.ts")]) to call bunExe() instead so it matches other tests that use
bunExe() (see other occurrences around bunExe() at lines 371 and 408) and
preserves existing arguments and options.

});

const { stdout, stderr, exitCode } = Bun.spawnSync([process.argv0, "--smol", "test", tempfile], {
const { stderr: stream, exited } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {

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🧹 Nitpick | 🔵 Trivial

Consider using bunExe() for consistency.

Same inconsistency as lines 89 and 147: consider using bunExe() instead of process.argv0 for consistency.

Suggested change
-        const { stderr: stream, exited } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {
+        const { stderr: stream, exited } = Bun.spawn([bunExe(), "--smol", "test", join(dir, "script.ts")], {
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
const { stderr: stream, exited } = Bun.spawn([process.argv0, "--smol", "test", join(dir, "script.ts")], {
const { stderr: stream, exited } = Bun.spawn([bunExe(), "--smol", "test", join(dir, "script.ts")], {
🤖 Prompt for AI Agents
In @test/js/bun/shell/leak.test.ts at line 235, Replace the direct use of
process.argv0 with the helper bunExe() to keep spawn invocation consistent; in
the Bun.spawn call that destructures { stderr: stream, exited } and currently
passes [process.argv0, "--smol", "test", join(dir, "script.ts")], swap
process.argv0 for bunExe() so the array becomes [bunExe(), "--smol", "test",
join(dir, "script.ts")] to match the other tests using bunExe().

@Jarred-Sumner
Jarred-Sumner merged commit bdc95c2 into main Jan 8, 2026
53 of 55 checks passed
@Jarred-Sumner
Jarred-Sumner deleted the jarred/speed-up-shell-leak-test branch January 8, 2026 05:31
@coderabbitai coderabbitai Bot mentioned this pull request Jan 8, 2026
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2 participants