? Writing Test Scripts in Postman

? Quick Overview

Postman allows you to write automated test scripts to validate API responses. These scripts run after a request is sent and help ensure correctness, reliability, and consistency of APIs using JavaScript and the built-in pm object.

? Key Concepts

• pm Object – Core Postman API for tests, variables, and responses
• Tests Tab – Section where test scripts are written
• Assertions – Conditions that must pass for a test to succeed
• Test Structure – Organizing tests for clarity and reuse

? Syntax / Theory

Postman test scripts are written in JavaScript and executed in a sandbox. The pm object provides methods to access request data, responses, environment variables, and assertion helpers.

• pm.test() – Define a test case
• pm.expect() – Write assertions
• pm.response – Access API response
• pm.environment – Work with environment variables

? Code Example(s)

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

// Validate a JSON response property
pm.test("Response has userId", function () {
const jsonData = pm.response.json();
pm.expect(jsonData).to.have.property("userId");
});

? Live Output / Explanation

? Interactive Example / Visual Flow

The basic execution flow in Postman:

1. Request is sent
2. Response is received
3. Test scripts execute
4. Results appear in the Tests tab

// The Active Test Script
pm.test("Status code is 200", function () {
  pm.response.to.have.status(200);
});

? Use Cases

• Automated API testing
• Regression testing during development
• Validating response schemas
• CI/CD pipeline integration