tmux TDD Skill

Orchestrate Test-Driven Development in a tmux environment by reading test output directly from panes. Language agnostic.

Environment Layout

┌────────────────┬────────────────┐
│                │                │
│   Pane 0.0     │   Pane 0.1     │
│   Claude Code  │   Test Runner  │
│                │                │
└────────────────┴────────────────┘

• Pane 0.0: Claude Code (where you are)
• Pane 0.1: Test runner (cargo watch, pytest, jest, go test, etc.)

Instructions

Step 1: Check Current Test Status

Capture output directly from the test pane:

tmux capture-pane -t 0.1 -p -S -50

Options:

• -t 0.1: Target pane (test runner)
• -p: Print to stdout
• -S -50: Last 50 lines (use -S - for full history)

Step 2: Parse Test Results

Look for pass/fail patterns based on the language:

Rust (cargo test):

test result: ok. 6 passed; 0 failed
test result: FAILED. 4 passed; 2 failed
error[E0425]: cannot find value `x` in this scope

Python (pytest):

6 passed in 0.12s
2 failed, 4 passed in 0.15s
FAILED tests/test_app.py::test_add - AssertionError
E       assert 4 == 5

JavaScript (jest/vitest):

Tests:       6 passed, 6 total
Tests:       2 failed, 4 passed, 6 total
FAIL src/app.test.js
  ✕ should add numbers (5 ms)

Go (go test):

ok      mypackage    0.005s
FAIL    mypackage    0.005s
--- FAIL: TestAdd (0.00s)
    app_test.go:10: expected 5, got 4

Step 3: Make Code Changes

Edit the source files to fix failures. If using a watch mode, tests will automatically re-run.

Step 4: Verify Fix

Wait for tests to re-run, then capture pane again:

tmux capture-pane -t 0.1 -p -S -30

Step 5: Send Commands to Test Pane (if needed)

# Run command in test pane
tmux send-keys -t 0.1 "your-test-command" C-m

# Stop running process
tmux send-keys -t 0.1 C-c

Common Test Commands by Language

Language	Watch Mode	Single Run
Rust	cargo watch -x test	cargo test
Python	ptw or pytest-watch	pytest
JavaScript	jest --watch or vitest	jest or npm test
Go	gotestsum --watch	go test ./...
Ruby	guard	rspec

Quick Reference

Task	Command
Read test output	tmux capture-pane -t 0.1 -p -S -50
Full history	tmux capture-pane -t 0.1 -p -S -
Send command	tmux send-keys -t 0.1 "command" C-m
Stop process	tmux send-keys -t 0.1 C-c
List panes	tmux list-panes

TDD Workflow

1. RED: Write a failing test, verify it fails via pane capture
2. GREEN: Write minimal code to make it pass
3. REFACTOR: Clean up while keeping tests green

Always check test status before and after making changes.

Troubleshooting

Empty pane output?

• Test runner may not be running
• Check: tmux capture-pane -t 0.1 -p -S -5
• Restart the test watcher in pane 0.1

Can't connect to pane?

• Verify tmux session exists: tmux list-sessions
• List panes: tmux list-panes