? Assertions & Validations in Postman

? Quick Overview

Assertions and validations in Postman are used to verify API responses automatically. They help confirm that status codes, response bodies, headers, and response times meet expectations.

? Key Concepts

• Assertions validate API behavior
• Written using JavaScript in the Tests tab
• Use pm.expect() or pm.response
• Ensure reliability and correctness of APIs

? Syntax / Theory

Postman uses the Chai Assertion Library. Assertions are placed inside the Tests tab and executed after receiving the response.

// Basic structure of a Postman test script
pm.test("Test name", function () {
pm.expect(true).to.eql(true);
});

? Code Example(s)

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

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

// Validate response time is under 500ms
pm.test("Response time is acceptable", function () {
pm.expect(pm.response.responseTime).to.be.below(500);
});

? Live Output / Explanation

? Interactive Example

Click the Send button below to run the API request and execute the test scripts defined on the left.

? Use Cases

• API regression testing
• CI/CD pipeline validation
• Performance monitoring
• Data integrity checks