API TESTING

Slide 1: What is API Testing?

• API = Application Programming Interface

• API Testing = Validating the logic, performance, and reliability of APIs

• Usually done with tools like Postman, Newman, REST Assured, etc.

🧪 Slide 2: Types of API Testing

• Functional Testing – Does it return the correct output?

• Load Testing – Can it handle many requests?

• Security Testing – Is it protected from attacks?

• Validation Testing – Schema & response validation

• Error Handling – Does it fail gracefully?

🔧 Slide 3: Tools Used in API Testing

• Postman – GUI-based tool to send and test API requests

• Newman – Run Postman collections via CLI (automation)

• REST Assured – Java-based API testing library

• Swagger – API documentation and testing

• JMeter – For performance/load testing

•  1. API Testing Flow Diagram (Conceptual)

 ┌────────────────────┐
 │     Postman App    │
 └───────┬────────────┘
         │ Sends Request
         ▼
 ┌────────────────────┐
 │      API Server    │
 │ (e.g., UserService)│
 └───────┬────────────┘
         │ Sends Response
         ▼
 ┌────────────────────┐
 │   Postman Response │
 │  (Status, JSON, etc)│
 └────────────────────┘

✅ What happens:

• Postman sends your request (GET, POST, PUT, DELETE).

• The API server processes it.

• The server sends back a response (data + status code).

• Postman displays the result.

🧠 2. API Testing Lifecycle Diagram

 [Design Request]
       ↓
 [Set URL + Method]
       ↓
 [Add Headers / Auth]
       ↓
 [Add Request Body (if needed)]
       ↓
 [Send Request]
       ↓
 [View Response]
       ↓
 [Validate Response]
       ↓
 [Automate Tests]

⚙️ 3. Test Types Diagram

      ┌─────────────────────┐
      │     API Tests       │
      └─────────┬───────────┘
                │
   ┌────────────┼────────────┐
   │            │            │
Functional   Performance   Security
Testing       Testing       Testing

• Functional: Check if endpoints work (GET, POST, etc.)

• Performance: Test speed, load, and response time

• Security: Test tokens, authentication, and access control

📄 Slide 4: Common HTTP Methods in API Testing

• GET – Retrieve data

• POST – Submit new data

• PUT – Update existing data

• DELETE – Remove data

• PATCH – Partial updates

✅ Slide 5: What to Validate in API Testing

• Status codes (200, 201, 400, 401, 404, 500, etc.)

• Response time

• Response body (JSON/XML structure, fields)

• Headers (Content-Type, Authorization)

• Data consistency (in DB or cache)

🔁 Slide 6: Automation and CI/CD Integration

• Use Newman to run collections in CLI

• Integrate with Jenkins, GitHub Actions, or GitLab CI

• Generate test reports (HTML, JSON)

• Schedule automated API monitoring

Sample GET Request in Postman

API Endpoint

https://jsonplaceholder.typicode.com/posts/1

How to Set It Up in Postman

1. Open Postman.

2. Create a New Request.

3. Set method to GET.

4. Paste the URL:https://jsonplaceholder.typicode.com/posts/1

5. Click Send.

Expected Response

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit\nsuscipit..."
}

Adding a Basic Test Script

Go to the Tests tab and add:

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

pm.test("Response has title", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData).to.have.property("title");
});

 Sample PUT Request in Postman

API Endpoint

https://jsonplaceholder.typicode.com/posts/1

How to Set It Up in Postman

1. Open Postman.

2. Create a New Request.

3. Set method to PUT.

4. Paste the URL:https://jsonplaceholder.typicode.com/posts/1

5. Go to the Body tab → Select raw → Choose JSON.

6. Enter the JSON body:

{
  "id": 1,
  "title": "Updated Title",
  "body": "This is the updated content of the post.",
  "userId": 1
}

7. Click Send.

Expected Response

{
  "id": 1,
  "title": "Updated Title",
  "body": "This is the updated content of the post.",
  "userId": 1
}

Adding a Basic Test Script

Go to the Tests tab and add:

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

pm.test("Response title is updated", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData.title).to.eql("Updated Title");
});

Sample DELETE Request in Postman

API Endpoint

https://jsonplaceholder.typicode.com/posts/1

This endpoint simulates the deletion of a post with ID 1.

🔧 How to Set It Up in Postman

1. Open Postman.

2. Create a New Request.

3. Set the HTTP method to DELETE.

4. Enter the URL:

   https://jsonplaceholder.typicode.com/posts/1

5. Click Send.

✅ Expected Response

Upon successful deletion, the response should indicate that the resource was deleted. The status code is typically 200 OK or 204 No Content, and the response body may be empty or contain a confirmation message.

Example:

{}

🧪 Adding a Basic Test Script

To verify the success of the DELETE request, you can add a test script in the Tests tab:

pm.test("Status code is 200 or 204", function () {
    pm.expect(pm.response.code).to.be.oneOf([200, 204]);
});

This script checks that the response status code is either 200 or 204, indicating a successful deletion.

Sample POST Request in Postman

API Endpoint

https://jsonplaceholder.typicode.com/posts

This endpoint simulates creating a new post.

🔧 How to Set It Up in Postman

1. Open Postman.

2. Create a New Request.

3. Set the HTTP method to POST.

4. Enter the URL:

   https://jsonplaceholder.typicode.com/posts

5. Go to the Body tab → Select raw → Choose JSON.

6. Enter the JSON body:

   { "title": "My New Post", "body": "This is the content of the new post.", "userId": 1 }

7. Click Send.

✅ Expected Response

Upon successful creation, the response should include the newly created post's details, including an auto-generated id.

Example:

{
  "id": 101,
  "title": "My New Post",
  "body": "This is the content of the new post.",
  "userId": 1
}

🧪 Adding a Basic Test Script

To verify the success of the POST request, you can add a test script in the Tests tab:

pm.test("Status code is 201", function () {
    pm.response.to.have.status(201);
});

pm.test("Response contains new post id", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData).to.have.property("id");
});

This script checks that the response status code is 201 (Created) and that the response contains an id property.