Bruno API Testing

Bruno API Testing

Create and run API test collections using Bruno — a Git-first, offline-only API client that stores collections as plain files.

Format Selection

Bruno supports two file formats. Determine which to use:

• YAML (OpenCollection) — Default since Bruno v3.1. Uses .yml files and opencollection.yml root. Preferred for new projects.
• Bru (Legacy) — Uses .bru files and bruno.json root. Use only for existing Bru-format collections.

Detect format by checking the collection root: opencollection.yml → YAML, bruno.json → Bru.

For YAML format syntax details, see references/yaml-syntax.md. For Bru format syntax details, see references/bru-syntax.md.

Workflow

1. Create Collection Structure

Create the directory layout with the collection root file, environments, and organized request folders.

YAML format:

my-api-tests/
├── opencollection.yml          # REQUIRED: collection root
├── environments/
│   ├── Local.yml
│   ├── Staging.yml
│   └── Production.yml
├── Auth/
│   ├── folder.yml
│   └── Login.yml
└── Users/
    ├── folder.yml
    ├── Get Users.yml
    ├── Get User by ID.yml
    └── Create User.yml

Minimal opencollection.yml:

opencollection: 1.0.0

info:
  name: My API Tests

Bru format: Same structure but use bruno.json + .bru extensions. See references/bru-syntax.md.

2. Create Environment Files

YAML (environments/Local.yml):

variables:
  - name: baseUrl
    value: http://localhost:3000/api
  - name: apiKey
    value: ""
    secret: true

Bru (environments/Local.bru):

vars {
  baseUrl: http://localhost:3000/api
}

vars:secret [
  apiKey
]

3. Write Request Files with Tests

YAML format — a complete request with tests:

info:
  name: Get Users
  type: http
  seq: 1

http:
  method: GET
  url: "{{baseUrl}}/users"
  headers:
    - name: accept
      value: application/json
    - name: authorization
      value: "Bearer {{authToken}}"

runtime:
  assertions:
    - expression: res.status
      operator: eq
      value: "200"
    - expression: res.body
      operator: isArray
  scripts:
    - type: tests
      code: |-
        test("returns 200", function() {
          expect(res.status).to.equal(200);
        });

        test("returns array of users", function() {
          expect(res.body).to.be.an('array');
          expect(res.body).to.have.lengthOf.at.least(1);
        });

        test("each user has required fields", function() {
          res.body.forEach(user => {
            expect(user).to.have.property('id');
            expect(user).to.have.property('email');
          });
        });

settings:
  encodeUrl: true

Use assertions (declarative) for simple checks, tests scripts (Chai.js) for complex logic.

4. Chain Requests with Data Extraction

Extract data from one response and use it in subsequent requests:

YAML — Login request saving a token:

info:
  name: Login
  type: http
  seq: 1

http:
  method: POST
  url: "{{baseUrl}}/auth/login"
  body:
    type: json
    data: |-
      {
        "username": "{{username}}",
        "password": "{{password}}"
      }
  auth:
    type: none

runtime:
  scripts:
    - type: after-response
      code: |-
        bru.setEnvVar("authToken", res.body.access_token);
    - type: tests
      code: |-
        test("login successful", function() {
          expect(res.status).to.equal(200);
          expect(res.body).to.have.property('access_token');
        });

Then reference {{authToken}} in subsequent requests via Bearer {{authToken}}.

5. Run Tests with bru CLI

Install and run:

npm install -g @usebruno/cli

# Run entire collection
cd my-api-tests && bru run --env Local

# Run specific folder
bru run Auth --env Local

# Run with developer mode (for external packages, fs access)
bru run --env Local --sandbox=developer

# Filter by tags
bru run --tags=smoke --env Local

# Generate reports
bru run --env Local \
  --reporter-html results.html \
  --reporter-junit results.xml \
  --reporter-json results.json

# Pass secrets via CLI
bru run --env Local --env-var API_KEY=secret123

# Parallel execution
bru run --env Local --parallel

# Data-driven testing
bru run --csv-file-path data.csv --env Local

v3.0.0 breaking change: Default is now Safe Mode. Use --sandbox=developer for developer mode features.

6. Set Up CI/CD

See references/ci-cd.md for complete GitHub Actions workflows, matrix testing, and reporting patterns.

Minimal GitHub Actions workflow:

name: API Tests
on: [push, pull_request]

jobs:
  api-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: "20"
      - run: npm install -g @usebruno/cli
      - name: Run API Tests
        working-directory: ./my-api-tests
        env:
          API_KEY: ${{ secrets.API_KEY }}
        run: bru run --env CI --reporter-html results.html --reporter-junit results.xml
      - uses: actions/upload-artifact@v4
        if: always()
        with:
          name: test-results
          path: |
            ./my-api-tests/results.html
            ./my-api-tests/results.xml

Critical: Always set working-directory to the collection root in CI/CD.

Testing Patterns

Assertions (Declarative) — Use for Simple Checks

runtime:
  assertions:
    - expression: res.status
      operator: eq
      value: "200"
    - expression: res.body.success
      operator: eq
      value: "true"
    - expression: res.body.data
      operator: isJson
    - expression: res.headers.content-type
      operator: contains
      value: application/json

Operators vary slightly by Bruno version and editor surface. Check Bruno's current Assertions docs for the exact operator names supported by your version when writing declarative assertions.

Tests (Chai.js) — Use for Complex Validation

runtime:
  scripts:
    - type: tests
      code: |-
        test("status and structure", function() {
          expect(res.status).to.equal(200);
          expect(res.body).to.be.an('object');
          expect(res.body).to.have.all.keys('id', 'name', 'email');
        });

        test("validates email format", function() {
          expect(res.body.email).to.match(/^[\w\-.]+@([\w-]+\.)+[\w-]{2,4}$/);
        });

        test("response time acceptable", function() {
          expect(res.responseTime).to.be.below(2000);
        });

        test("pagination works", function() {
          expect(res.body.data).to.be.an('array');
          expect(res.body.meta.total).to.be.a('number');
          expect(res.body.meta.page).to.equal(1);
        });

For the complete JavaScript API (req, res, bru objects), see references/javascript-api.md.

Common Mistakes

1. Missing opencollection.yml (YAML) or bruno.json (Bru) at collection root
2. Using meta: instead of info: in YAML request files
3. Using script type test instead of tests (plural)
4. Putting request-level fields (http:, method:) in opencollection.yml
5. Forgetting working-directory in CI/CD steps
6. Committing secrets — use secret: true in env files + CI/CD secrets
7. Using |- for body data is required in YAML to preserve JSON formatting
8. Missing seq number in info: — controls execution order
9. Relying on folder.yml script/auth inheritance in CLI — Bruno's Sandwich execution order (Collection → Folder → Request) for before-request scripts may work in the Bruno GUI, but @usebruno/cli does NOT reliably inherit folder.yml scripts or auth settings to individual test files. Always add before-request scripts and auth blocks directly to each request file that needs them. The folder.yml is useful for documentation and GUI users, but CLI-driven tests must be self-contained.

Script Execution Order

Bruno supports two script flows:

1. Sandwich (default): Collection before-request → Folder before-request → Request before-request → Request is sent → Request after-response → Folder after-response → Collection after-response
2. Sequential: Collection before-request → Folder before-request → Request before-request → Request is sent → Collection after-response → Folder after-response → Request after-response

Request assertions and request tests run after the post-response scripts.

⚠️ CLI Inheritance Caveat

The Sandwich/Sequential script execution order described above applies to Bruno GUI only. When running tests with @usebruno/cli (the CLI runner used in CI/CD), folder-level before-request scripts and auth settings are NOT reliably inherited by individual request files.

Impact: If a folder.yml contains a before-request script (e.g., to skip requests when an environment variable is "false"), request files in that folder will NOT inherit this logic when run via CLI.

Workaround: Duplicate the before-request logic into each individual request file that needs it:

# In each request file that needs conditional skip:
runtime:
  scripts:
    - type: before-request
      code: |-
        const featureAvailable = bru.getEnvVar("featureAvailable");
        if (featureAvailable === "false") {
          bru.runner.skipRequest();
        }
    - type: tests
      code: |-
        test("returns 200", function() {
          expect(res.status).to.equal(200);
        });

Same applies to auth: Set http.auth in each request file, not just folder.yml.

Variable Precedence (Highest to Lowest)

1. Runtime variables (bru.setVar())
2. Request variables
3. Folder variables
4. Collection variables
5. Environment variables

Use bru.getGlobalEnvVar() for global environment values and bru.getProcessEnv() for OS process environment variables. They are not documented as part of the standard collection variable precedence chain.

References

• YAML Syntax — Complete OpenCollection YAML format for requests, bodies, auth, headers, params, environments, folders, collections
• Bru Syntax — Legacy .bru file format reference
• JavaScript API — Full req, res, bru object API with runner control, cookies, utilities
• CI/CD Integration — GitHub Actions workflows, report generation, matrix testing, environment secrets