Integrate Tarn into your CI pipeline.

GitHub Actions

Copy this workflow into .github/workflows/tarn.yml:

name: API Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - name: Install Tarn
        run: curl -fsSL https://raw.githubusercontent.com/NazarKalytiuk/tarn/main/install.sh | sh
      - name: Validate YAML
        run: tarn validate
      - name: Run tests
        run: tarn run --format json --json-mode compact --no-progress
        env:
          BASE_URL: ${{ secrets.API_BASE_URL }}
          API_KEY: ${{ secrets.API_KEY }}

Validate before run

Run tarn validate at the start of CI to catch YAML and config issues before execution:

$ tarn validate
$ tarn validate --format json

Failing the pipeline

tarn run exits non-zero when any test fails. For JSON output, check summary.status in the report:

$ tarn run --format json --json-mode compact --no-progress
# exits 1 if any test fails

Saving JSON report as artifact

- name: Run tests
  run: tarn run --format json=reports/run.json --no-progress
- name: Upload report
  uses: actions/upload-artifact@v4
  with:
    name: tarn-report
    path: reports/run.json

The JSON report contains structured failure data including failure_category, error_code, request and response payloads, and remediation_hints — ideal for post-processing in CI.

Using environment secrets

Pass secrets via env vars. They override tarn.env.yaml values due to the priority chain:

- name: Run tests
  run: tarn run
  env:
    BASE_URL: ${{ secrets.API_BASE_URL }}
    API_KEY: ${{ secrets.API_KEY }}

Using named environments

$ tarn run --env prod
$ tarn run --env staging

Define each environment's variables in tarn.env.prod.yaml and tarn.env.staging.yaml.

Using --var for overrides

$ tarn run --var base_url=https://staging.example.com --var api_key=test123

The --var flag has the highest priority in the variable resolution chain, above shell env and env files.

Format check in CI

$ tarn fmt --check tests/
# exits 1 if any file needs formatting

Add this as a lint step early in your pipeline. It shares the same formatter engine as the LSP's textDocument/formatting, so passing --check means byte-identical output to "Format Document" in any editor.

Other CI systems

Best practices for CI

• Always run tarn validate before tarn run
• Use --no-progress in CI for clean output
• Use --format json --json-mode compact for machine parsing
• Use deterministic faker seed: TARN_FAKER_SEED=42 tarn run
• Pass secrets via CI env vars, not in tarn.env.yaml
• Format gating: tarn fmt --check in a lint step