oss-write-tests

Write Tests

Add tests for untested code — the highest-value, lowest-risk first contribution. You need to understand the code deeply without modifying it, and the result is almost always welcome.

Purpose

Test contributions teach you a codebase faster than any other contribution type. You read every function signature, trace every code path, and understand every edge case — without the pressure of changing production code. Maintainers love test PRs because they reduce risk for everyone. This skill guides you through finding untested code, learning the repo's test conventions, and writing tests that a maintainer would write themselves.

When to Use

• Making your first contribution to a repo and want something low-risk
• You've found code with no tests or poor coverage
• You want to learn a codebase deeply before tackling a bug or feature
• NOT when writing tests as part of a bug fix — use oss-contribute for that
• NOT when the repo has no test infrastructure at all — that's a different conversation with maintainers

Prerequisites

• Repo forked, cloned, and set up (from oss-prep-to-contribute)
• Test suite runs successfully (make test, npm test, pytest, etc.)
• User has a target module or area in mind

Process

1. Identify untested code

Find code that lacks test coverage. Use multiple signals — don't rely on just one.

# Check if the repo has coverage reports
ls coverage/ htmlcov/ .coverage *.lcov 2>/dev/null

# Find source files without corresponding test files
# Adapt the pattern to the repo's naming convention
find src/ -name "*.ts" | while read f; do
  test_file=$(echo "$f" | sed 's|src/|tests/|; s|\.ts$|.test.ts|')
  [ ! -f "$test_file" ] && echo "No tests: $f"
done

# Find public functions without any test assertions
grep -rn "export function\|def \|pub fn\|func " src/ --include="*.ts" --include="*.py" --include="*.rs" --include="*.go" | head -30

Then cross-reference against test files:

# What symbols are already tested?
grep -rn "describe\|it(\|test(\|def test_\|func Test" tests/ test/ __tests__/ spec/ | head -30