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Postman API Testing Tips

How To Use Postman For Automated Testing

API Testing Blog

Leveraging Postman for Automated API Testing

Postman is a powerful tool for API testing, offering a wide range of features for both manual and automated testing. Here’s a comprehensive guide to using Postman for automating your API tests:

1. Creating and Organizing Tests

1.1. Creating Test Collections:

Postman collections allow you to group related API requests and their associated tests. This facilitates organization and reusability.

1.2. Adding Tests to Requests:

Each request within your collection can have dedicated tests. In the “Tests” tab of the request editor, you can write code using JavaScript to verify various aspects of the API response.

Example: Verifying Status Code and Response Body:

pm.test("Status code is 200", function () {
    pm.response.to.have.status(200);
});


pm.test("Response body contains 'success'", function () {
    pm.expect(pm.response.text()).to.include('success');
});

2. Writing Assertions and Using Variables

2.1. Writing Assertions:

Postman provides a wide array of assertion methods using the pm object. These methods allow you to check:

  • Status codes: pm.response.to.have.status(200)
  • Response body content: pm.expect(pm.response.text()).to.include('message')
  • Headers: pm.expect(pm.response.headers.get('Content-Type')).to.eql('application/json')
  • Length of response: pm.expect(pm.response.text()).to.have.lengthOf(10)
  • JSON properties: pm.expect(pm.response.json().message).to.eql('successful')

2.2. Using Variables:

Postman allows you to define and use variables within your tests, requests, and collections. This helps in creating dynamic and reusable tests.

Example: Using Environment Variables:

pm.test("Verify Authorization Token", function () {
    pm.expect(pm.response.json().token).to.eql(pm.environment.get("authToken"));
});

3. Automating Test Execution

3.1. Running Tests via Runner:

The Postman Runner allows you to execute your tests in a controlled and automated manner. You can select specific collections or individual requests to run.

3.2. Using Newman Command Line Tool:

Newman is a command line tool provided by Postman for executing tests and generating reports. It allows you to automate test execution as part of your CI/CD pipeline.

Example: Running Test Collection with Newman:

Terminal window
newman run collection.json -e environment.json

4. Generating and Analyzing Reports

4.1. Using Postman Monitors:

Postman Monitors allow you to schedule regular automated test runs and receive reports on their results. This helps in monitoring API health and identifying potential issues.

4.2. Generating Reports with Newman:

Newman can be used to generate HTML reports summarizing test execution results. These reports can be integrated into your CI/CD pipelines for better visibility.

Example: Generating Report with Newman:

Terminal window
newman run collection.json -e environment.json -r html -o report.html

5. Best Practices for Postman Automated Testing

5.1. Modular Test Structure:

Break down your tests into smaller, manageable modules. This improves code readability and reusability.

5.2. Clean and Descriptive Code:

Prioritize clear and well-documented tests for ease of maintenance and understanding.

5.3. Data-Driven Testing:

Use data files to parameterize your tests, reducing repetition and enabling efficient testing of various scenarios.

5.4. Integrated into CI/CD Pipeline:

Automate test execution within your CI/CD pipeline for continuous integration and seamless feedback.

By applying these principles and leveraging the capabilities of Postman, you can effectively automate your API testing process, leading to more comprehensive and efficient testing efforts.

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