API Request Components

API Request Components – Headers, Path Params & Query Params

Every API request is built from multiple components.
Most API automation bugs happen because one of these components is misunderstood or misused.

This section explains each component clearly, with tester-focused rules.

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1️⃣ URL & Endpoint (Quick Recap)

Example:

GET /users/101/orders?status=SUCCESS

Breakdown:

• /users/101/orders → Path (identifies the resource)
• ?status=SUCCESS → Query parameters (filter or modify the response)

Why It Matters

The URL structure defines how you interact with the API. Misplacing components (e.g., using query params instead of path params) can lead to unexpected behavior.

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2️⃣ Path Parameters

What are Path Params?

Path parameters identify a specific resource.

Example:

GET /users/101

Here:

• 101 is a path parameter that identifies the user.

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Characteristics of Path Params

Aspect	Behavior
Purpose	Identify resource
Mandatory	✅ Yes
Order matters	✅ Yes
Part of URL	✅ Yes

Why It Matters

Path parameters are essential for CRUD operations. They must be correctly formatted and validated.

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Automation Use Cases

• Fetch specific user (GET /users/{id}).
• Update specific order (PUT /orders/{id}).
• Delete a resource (DELETE /users/{id}).

Validation Checklist

• Correct resource returned.
• 404 Not Found for invalid IDs.

Code Snippet: Validating Path Params

// RestAssured example
Response response = given()
    .when()
    .get("/users/101");

response.then().statusCode(200);
response.then().body("id", equalTo(101));

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Common Path Param Mistakes ❌

• Passing invalid ID format: Ensure IDs match expected formats (e.g., numeric, UUID).
• Using query param instead of path param: Example: /users?id=101 instead of /users/101.
• Hardcoding IDs across tests: Use dynamic values or externalize IDs.

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3️⃣ Query Parameters

What are Query Params?

Query parameters sort or filter or modify the response and those are always identified with ?

Example:

GET /orders?status=SUCCESS&limit=10

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Characteristics of Query Params

Aspect	Behavior
Purpose	Filter, sort, paginate
Mandatory	❌ Usually optional
Order matters	❌ No
Part of URL	✅ Yes

Why It Matters

Query parameters allow testers to simulate real-world scenarios like pagination, filtering, and sorting.

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Common Automation Use Cases

• Pagination (page=2, limit=10).
• Filtering (status=SUCCESS, type=ACTIVE).
• Sorting (sort=createdDate, order=asc).

Real-World Example

Fetching paginated orders:

GET /orders?page=2&limit=10

Code Snippet: Validating Query Params

// RestAssured example
Response response = given()
    .queryParam("status", "SUCCESS")
    .queryParam("limit", 10)
    .when()
    .get("/orders");

response.then().statusCode(200);
response.then().body("size()", equalTo(10));

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Common Query Param Mistakes ❌

• Forgetting encoding: Special characters in query params must be URL-encoded.
• Assuming order matters: Query params are unordered; /orders?status=SUCCESS&limit=10 is the same as /orders?limit=10&status=SUCCESS.
• Missing default values: Validate behavior when query params are omitted.
• Hardcoding pagination: Use dynamic values for scalability.

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4️⃣ Headers (VERY IMPORTANT)

What are Headers?

Headers represent the meta-data associated with the API request and response. We are sending Additional details to API to process our request.

• Headers carry metadata about the API request.

Example:

Headers:
Content-Type: application/json
Authorization: Bearer token

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Common Headers Testers Must Know

Header	Purpose
Content-Type	Format of request body
Accept	Expected response format
Authorization	Auth token
Cache-Control	Caching behavior
Custom headers	App-specific logic

Why It Matters

Headers often determine whether the request succeeds or fails. Missing or incorrect headers are a common source of bugs.

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Content-Type vs Accept (Interview Favorite)

Header	Meaning
Content-Type	Format of request body (e.g., JSON).
Accept	Expected response format (e.g., JSON).

Real-World Example

Sending JSON data and expecting JSON response:

POST /users
Headers:
Content-Type: application/json
Accept: application/json
Body:
{
  "name": "John",
  "email": "john@example.com"
}

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Header Automation Mistakes ❌

• Missing Content-Type: Leads to 415 Unsupported Media Type.
• Wrong token placement: Use Authorization: Bearer <token>, not Bearer: <token>.
• Hardcoding auth headers: Externalize tokens for scalability.
• Ignoring custom headers: Validate app-specific headers like X-Request-ID.

Code Snippet: Validating Headers

// RestAssured example
Response response = given()
    .header("Content-Type", "application/json")
    .header("Authorization", "Bearer token")
    .when()
    .get("/users/101");

response.then().statusCode(200);

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5️⃣ Request Body (Preview)

The body contains the payload sent to the server.

Example:

{
  "userId": 101,
  "amount": 500
}

We’ll cover body & JSON deeply in the next section.

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Parameter Comparison (Important)

Aspect	Path Param	Query Param
Purpose	Identify resource	Filter data
Mandatory	Yes	Usually No
Order matters	Yes	No
Used for	CRUD	Search & pagination

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Automation Best Practices ✅

• Always verify correct param usage.
• Externalize IDs and params (e.g., use environment variables or config files).
• Log full request on failure (headers, path, query params, body).
• Avoid hardcoding values.
• Validate negative param scenarios (e.g., invalid IDs, missing headers).

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Interview-Ready Questions

Q: Difference between path and query parameters?
A: Path identifies resource; query filters data.

Q: What happens if Content-Type is missing?
A: Server may reject or misinterpret request.

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Key Takeaways 🎯

• API requests have multiple components: URL, path params, query params, headers, and body.
• Path params identify resources.
• Query params filter results.
• Headers carry metadata & auth.
• Small mistakes cause major failures.