API Testing with Postman Course Notes

Instructor Introduction

• Name: Valentine
• Background: Software developer passionate about teaching APIs.
• Course Goal: Explain API testing using Postman in an easy-to-understand way.

Course Overview

• Understand what Postman is and why it is essential for API testing.
• Learn to interact with APIs and write API tests.
• Explore automation of the testing process.
• Hands-on experience with API assignments for practice.

Understanding APIs

• Definition: An API (Application Programming Interface) is an interface to a server that provides data or functionality.
• Analogy: Like a power outlet that accepts any device with the right plug specifications, APIs communicate data based on set specifications.
• Documentation: Always refer to API documentation to understand its functionalities.

Getting Started with Postman

• Postman is a tool for interacting with web-based APIs through the internet.
• Installation: Two options to use Postman:
  • Browser application: postman.com
  • Standalone app (requires installation).
• Account Setup: Create an account, keeping in mind updates in Postman versions may occur.

Using Postman

Interface and First API Request

• Set a black theme for better visibility (gear icon > themes).
• Example API: Book ordering API
• Making the First Request: Status Endpoint
  • URL format: [Base URL]/status
  • HTTP Method: GET
  • Expected Response: 200 (status OK).

Understanding HTTP Requests/Responses

• Request: Components
  • URL (API address)
  • Request method (GET, POST)
  • Headers & Body (for POST requests)
• Response: Components
  • Status code (e.g., 200, 400)
  • Response body (data returned from the server)

Saving Requests and Collections

• Save frequently used requests in a collection for better organization.
• Variables can be created to avoid hardcoding values, thus making requests more flexible.

API Data Filtering and Query Parameters

• Using Query Parameters with GET requests for additional filtering.
• Example: Adding ?type=fiction to filter requests.
• Monitor the status codes: 200 (OK), 400 (Bad Request), etc.

Ordering Books: Path Parameters

• Order Book Endpoint: Specify book ID in the URL.
• Use variable for book ID for greater flexibility.

Interacting with Books API

• Using Postman to retrieve available books, order books, and check individual book details based on IDs.
• Handling responses and recording order IDs for future requests.

Authentication and Authorization

• Some API requests require authentication (e.g., using an access token).
• Ensure to configure authorization correctly in the headers of requests.

Writing Tests in Postman

• Writing JS Tests: Automate validation of HTTP responses using JavaScript in Postman's Tests section:
  • Check if the response status is correct (using pm.response.to.have.status(200)).
  • Ensure returned data is as expected (using pm.expect).

Automating Tests with Newman

• Newman: CLI tool for running Postman collections to automate tests.
• Install Node.js to set up Newman.
• Export the Postman collection in JSON format for running tests.
• Generate reports from Newman executions (CLI and HTML formats).

Monitoring with Postman

• Set up Monitors to run collections automatically at defined intervals (daily, weekly).
• Review execution history and results.

Practical Assignments Throughout the Course

• Create various requests, handle responses, and troubleshoot issues.
• Explore different endpoints, experiment with query parameters, and test error handling.
• Document expectations for the expected behavior of the API through written tests.

Further Learning

• Consider exploring data-driven testing with external files and deeper concepts in Postman usage.
• Links to additional tutorials in course notes for advanced subjects.

Conclusion

• Emphasis on real-world applicability and practical understanding of APIs.
• Encouragement to dive deeper into testing and development with APIs.
• Express gratitude for participation and invite further exploration of API testing.