The problem
Every developer knows this pain:
- Clone a repo
- Want to run the tests
- Open the README
- Scroll... scroll... find a "Development" section... maybe
- Figure out it's
pnpm test(notnpm test, notyarn test) - Run it wrong anyway because you needed
pnpm installfirst
Multiply this by every repo you touch. Every PR you review. Every onboarding.
I got tired of it.
The solution: rex
git clone https://github.com/some/repo
cd repo
rex test
That's it. Rex looks at your project files, detects the stack, and runs the correct command. No config. No setup. No reading anything.
How it works
Rex reads files in your project root:
| File found | Stack detected |
rex test runs |
|---|---|---|
go.mod |
Go | go test ./... |
package.json + pnpm-lock.yaml
|
Node + pnpm | pnpm test |
Cargo.toml |
Rust | cargo test |
pyproject.toml + uv.lock
|
Python + uv | uv run pytest |
composer.json + artisan
|
PHP + Laravel | php artisan test |
Gemfile + app/
|
Ruby + Rails | bundle exec rails test |
pom.xml |
Java + Maven | mvn test |
build.gradle |
Java + Gradle | ./gradlew test |
build.zig |
Zig | zig build test |
mix.exs |
Elixir | mix test |
Makefile |
Make | make test |
Justfile |
Just | just test |
12 ecosystems. It also detects which package manager you use by looking at lockfiles.
Demo
$ cd my-go-project/
$ rex
my-go-project
stack go
commands
rex test go test ./...
rex run go run ./cmd/server
rex build go build ./...
rex deps go mod download
rex fmt gofmt -w .
rex lint go vet ./...
$ rex test
> go test ./...
ok github.com/example/app 1.2s
The > arrow always shows exactly what rex will run. Full transparency.
All the verbs
| Command | What it does |
|---|---|
rex test |
Run tests |
rex run |
Start the app / dev server |
rex build |
Build the project |
rex deps |
Install dependencies |
rex clean |
Remove build artifacts |
rex fresh |
clean, deps, build in sequence |
rex fmt |
Format code |
rex lint |
Lint code |
rex clone <url> |
Clone + detect + install deps in one command |
rex init |
Generate rex.toml for your team |
rex doctor |
Diagnose environment issues |
Killer feature: rex clone
rex clone https://github.com/someone/project
# cloning...
# detected: node + pnpm
# deps: pnpm install
# ready! cd project && rex run
From URL to working project in one command. No README needed.
Monorepo support
Rex auto-detects monorepos (packages/, apps/, services/):
$ rex
my-monorepo (monorepo)
workspace 3 sub-projects detected
packages/api node + pnpm
packages/web node + pnpm
services/auth go
Team workflow: rex init
rex init
# created rex.toml (go project)
Generates a rex.toml from detected commands. Commit it. Now every teammate runs the same commands without asking.
.env loading
Rex automatically loads .env files before running commands. No extra tools needed.
Why I built this
I maintain projects across Go, Node, Python, and Rust. I context-switch between repos dozens of times per day. The cognitive load of remembering pnpm test vs go test ./... vs cargo test is small individually, but it adds up.
Rex makes every repo feel the same:
rex test # always works
rex run # always works
rex build # always works
It's the muscle memory tax I no longer pay.
Technical details
- Single binary, no runtime, no dependencies
- Written in Go, cross-platform
- Less than 50ms startup, faster than your shell prompt
- Zero network calls, fully offline
- Correct exit codes, works in CI
- Shell completions for bash, zsh, fish
- Apache 2.0 license
- Mentioned in Awesome Go
Install
# Homebrew (macOS/Linux)
brew tap rexrun-dev/tap && brew install rex
# Go
go install rexrun.dev/rex/cmd/rex@latest
Or grab a binary from GitHub Releases.
Links
- GitHub: github.com/rexrun-dev/rex
- Website: rexrun.dev
If this solves a pain you've felt, star the repo. If you want a stack added, open an issue.