API testing mainly focuses on understanding what APIs are and why testing them is crucial for Software application development. This section sets the stage for the rest of the document by outlining the importance of API testing ensuring robust and reliable software In this article we explain Test Cases For API Testing with related examples.

What is API Testing?

API testing involves testing application interfaces directly and as part of integration testing to determine if they meet functionality, reliability performance, and security expectations. API testing is concerned with the business logic layer of the software architecture, as opposed to UI testing, which is more concerned with the appearance and feel of the program.

Test Cases For API Testing For Each Category

Here we cover categories of API testing such as functional testing, load testing, security testing, and more. Here we provide examples of test cases that can be created for each category to ensure comprehensive API testing.

Functional Testing

• Verify that the API returns the correct response for valid input
• Check that the API handles invalid input correctly.

Loading Testing

• Test the APIs performance under heavy load conditions
• Measure response times during peak usage.

Security Testing

• Ensure the API is protected against unauthorized access.
• Verify the data transmission is encrypted.

Generic Test Cases for API Testing

Here are some generic test cases for API testing:

• Input Validation Tests: Ensure the API handles valid inputs correctly.
• Authentication and Authorization Tests: Verify that authentication mechanisms work as expected (e.g., tokens, API keys).
• HTTP Method Tests: Test each supported HTTP method (GET, POST, PUT, DELETE) to verify they perform the expected actions.
• Response Validation Tests: Validate the structure and content of API responses (e.g., JSON schema validation).
• JSON API: Send requests and verify the JSON response format matches the expected schema.
• XML API: Similarly, validate XML responses against their schema.
• XML Schema Validation: Send requests and validate XML responses against their defined XML schema.
• JSON Schema Validation: Validate JSON responses against their JSON schema to ensure correct structure and data types.
• Validate Response Headers: Verify that the API response includes appropriate headers (e.g., Content-Type, Cache-Control) with correct values.
• End-to-End CRUD Flow: Validate the complete CRUD operations (Create, Read, Update, Delete) for application APIs to ensure data integrity and functionality.
• Database Integrity Test Cases: Verify that API operations maintain database integrity, such as checking for correct data insertion, updates, and deletions.

How To Write Test Cases For API Testing

Here we provide step by step guide on how to write effective test cases for API testing. It includes tips on understanding API requirements defining test objects and appropriate tools for testing manually.

Understand the API Requirements

• Study the API documentation.
• Identify the input parameters and expected outputs.

Define Test Objectives

• Determine what needs to be tested.
• Set clear and measurable goals.

Use Appropriate Tools

• Select tools like Postman, SoapUI or JUnit for testing.
• Write test cases where possible.

Test Case Template For API Testing

Providing a standardized templates helps maintain consistency and ensures all necessary details are covered in each test case. The template should include sections for the test case ID, description, preconditions, test steps, expected results and actual results.

Example:

{
  "username": "[email protected]"
}

{ }

{
  "username": "[email protected]",
  "password": "test"
}

{
  "username": "[email protected]",
  "password": "test"
}