Report · marked 26 Aug 2026
jestjs/jest
Solid foundations, held back in a few specific places.
TypeScript · 45,472 stars · 3,560 files · branch main
70
/100
B+
Instructions
14/27Whether the repo tells an agent how to behave before it starts guessing. Losing marks on agent instruction file and instruction quality.Setup
14/20Whether an agent can install the project and get it running without a human. Losing marks on environment config and reproducible environment.Verification loop
25/25Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy. Full marks.Context economy
8/20Whether the repo fits in a context window, or fights it. Losing marks on no committed build output and file sizes fit in context.Navigability
10/10How quickly anything new can orient itself. Full marks.
Higher is better. Accent marks what is costing you most.
Fix these first
01
Instruction quality
Worth fixing: it's under 200 characters, which is closer to a placeholder than instructions; it never states a build, test, or run command; has no code blocks.
02
File sizes fit in context
A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.
03
Environment config
Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.
The full marking
Every deduction below names the file or setting it came from.
Instructions 14/27 C+
Whether the repo tells an agent how to behave before it starts guessing.
✗Agent instruction file
9/12
CLAUDE.md is present, but not the vendor-neutral AGENTS.md.
Rename or symlink to AGENTS.md so tools other than one vendor's can read it. Keeping CLAUDE.md alongside it costs nothing.
Also found: Copilot instructions
✗Instruction quality
2/12
Present but too thin to change an agent's behavior.
Worth fixing: it's under 200 characters, which is closer to a placeholder than instructions; it never states a build, test, or run command; has no code blocks.
uses headings, so an agent can skim it
✓README as an entry point
3/3
README has a clear getting-started section.
Setup 14/20 B+
Whether an agent can install the project and get it running without a human.
✓Deterministic install
6/6
yarn.lock pins the dependency tree.
Found yarn.lock
✓Discoverable commands
6/6
Commands are declared where an agent will look for them.
package.json scripts (build-clean, build, build:js, build:ts, bundle:ts, check-changelog…)
scripts/ directory
✗Environment config
0/4
Nothing documents the environment this needs. An agent will get a runtime error it can't diagnose.
Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.
✓Pinned runtime version
2/2
The language runtime version is pinned.
package.json engines.node ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0
✗Reproducible environment
0/2
No container or devcontainer definition.
A Dockerfile or devcontainer removes an entire class of 'it won't install' failures.
Verification loop 25/25 A+
Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy.
✓Tests exist
8/8
1644 test files against 2263 source files.
e.g. benchmarks/test-file-overhead/0.test.js, e2e/__tests__/__snapshots__/asyncAndCallback.test.ts.snap, e2e/__tests__/__snapshots__/beforeAllFiltered.ts.snap
✓Test command is discoverable
7/7
An agent can find and run `npm run test`.
✓Continuous integration
4/4
11 GitHub Actions workflows define what "passing" means.
✓Lint and format rules
3/3
eslint.config.mjs encodes the house style.
✓Static type checking
3/3
Strict type checking is on, which catches a whole class of agent mistakes before they run.
Context economy 8/20 C
Whether the repo fits in a context window, or fights it.
✗No committed build output
3/6
Generated output is committed: node_modules/.
Add these to .gitignore and `git rm -r --cached` them. Generated files pollute search results, so an agent grepping for a function finds the compiled copy and edits the wrong file.
✓.gitignore hygiene
3/3
.gitignore covers 64 patterns.
✗File sizes fit in context
0/6
1 source file is over 100KB.
A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.
.yarn/releases/yarn-4.18.0.cjs — 3696KB
✗Repository weight
2/5
About 323MB checked out. Large enough that cloning and searching are both slow.
Large binaries and vendored trees slow every operation an agent performs. Git LFS or a separate assets repo keeps the working tree navigable.
Here is your AGENTS.md
Drafted from what is actually in this repository: the install
command from your lockfile, the commands you already declare, your real directory layout. Anything
marked TODO needs a person. Save it at the root as AGENTS.md.
# AGENTS.md Delightful JavaScript Testing. ## Setup ``` yarn install ``` ## Commands ``` yarn build # produce a build yarn test # run the test suite, must pass before any commit yarn typecheck # type check without emitting yarn lint # lint yarn build-clean yarn build:js yarn build:ts yarn bundle:ts ``` ## Layout - `e2e/` 1140 source files - `packages/` 1003 source files - `examples/` 82 source files - `scripts/` 15 source files - `website/` 13 source files - `benchmarks/` 2 source files ## Conventions - Tests live alongside the code they cover, following `benchmarks/test-file-overhead/0.test.js`. - TypeScript runs in strict mode. Type errors are the fastest feedback available, so do not weaken it. - CI defines what passing means. See `.github/workflows/check-changelog.yml`, and keep it green. - TODO: add the two or three conventions a newcomer always gets wrong here. ## Gotchas - `.yarn/releases/yarn-4.18.0.cjs` is 3696KB. It will not fit comfortably in context, so read it in parts. --- Drafted by agentreadme.com from what is in this repository. Everything marked TODO needs a human. Check it in as AGENTS.md at the root.
Open the raw markdown
or
curl -o AGENTS.md agentreadme.com/draft/jestjs/jest.md
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Think this mark is wrong?
Every deduction above names the file it came from, so this can be settled by looking. If a check missed something, that is a rule worth fixing.