Postman API
Testing Tutorial

Think of it like a remote control for APIs. Instead of building a full app to test a feature, you use Postman to directly talk to the server.

• →
  Test APIs independently No need to wait for UI. Test backend directly.
• →
  Find bugs faster Test edge cases — empty data, invalid inputs, wrong tokens.
• →
  Save and reuse Save API calls in collections and run anytime.
• →
  Automate tests Write scripts to auto-validate responses.

1. 1
   Client sends Request Postman sends request to server — URL, method, headers, optional body.
2. 2
   Server processes Server receives, processes logic, fetches data from DB.
3. 3
   Server sends Response Returns status code (200, 404, 500) + body (usually JSON).

// Response from GET /users/1
{
  "id": 1,
  "name": "Priya Sharma",
  "email": "priya@example.com",
  "role": "QA Engineer"
}

The HTTP Method tells the server WHAT you want to do with the data.

• G
  GET — Fetch data Does NOT change anything. GET /users → returns all users.
• P
  POST — Create new Sends data to create a record. Response: 201 Created.
• U
  PUT — Full replace Replaces entire existing record with new data.
• PA
  PATCH — Partial update Only updates fields you send. Others stay unchanged.
• D
  DELETE — Remove Deletes the resource. Response: 200 or 204.

1. 1
   Open Postman Click + to create a new request tab.
2. 2
   Select GET Keep method as GET (default).
3. 3
   Enter URL: https://jsonplaceholder.typicode.com/users
4. 4
   Click Send Hit the blue Send button.
5. 5
   See Response Status 200 OK + JSON list of 10 users appears below.

[
  {
    "id": 1,
    "name": "Leanne Graham",
    "email": "Sincere@april.biz"
  }
  // 9 more users...
]

1. 1
   Method = POST. URL: https://jsonplaceholder.typicode.com/posts
2. 2
   Headers tab: Key = Content-Type, Value = application/json
3. 3
   Body tab → raw → JSON → paste JSON below
4. 4
   Click Send

{
  "title": "My First Post",
  "body": "This is the content",
  "userId": 1
}

{
  "id": 101,
  "title": "My First Post",
  "userId": 1
}

1. 1
   Status Code GET→200, POST→201, DELETE→200/204?
2. 2
   JSON Structure All required fields present? Names correct?
3. 3
   Data Types Is id a number? Is active a boolean? Is email a string?
4. 4
   Values Did the data you sent come back correctly?
5. 5
   Response Time Under 2000ms = good. Above 5000ms = bug.
6. 6
   Error Messages "Email is required" ✅ vs "Error 0x1A" ❌

1. 1
   Click Environments (eye icon, top right) → Add → Name it "Development".
2. 2
   Add: Key = baseUrl, Value = https://jsonplaceholder.typicode.com
3. 3
   Save → Select this environment from dropdown.
4. 4
   In URL bar type: {{baseUrl}}/users — Postman replaces it auto!

1. 1
   Click New → Collection → Give it a name.
2. 2
   Save requests inside the collection folder.
3. 3
   Click ▶ Run → Collection Runner opens.
4. 4
   Click Run — all requests run in sequence, show ✅ pass / ❌ fail.

1. 1
   Login first — POST /login with credentials. Server returns a token.
2. 2
   Copy token — From response body, copy the token string.
3. 3
   Authorization tab → Bearer Token → Paste token.
4. 4
   Or Headers tab: Key = Authorization, Value = Bearer your_token

# Requires Node.js installed
npm install -g newman
npm install -g newman-reporter-html

1. 1
   Export Collection: Right-click collection → Export → JSON file.
2. 2
   Export Environment: Click environment → Export → JSON file.
3. 3
   Run Newman from terminal:

newman run collection.json \
  -e environment.json \
  --reporters cli,html \
  --reporter-html-export report.html