API Interview Questions and Answers (Level-1)

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1. What are the different API methods you have tested?

Answer:

In API testing, I have tested several important HTTP methods that allow interaction with server resources. Each method serves a different purpose:

• GET:
  
  • Retrieves data from the server without modifying it.
    
  • It is a safe and idempotent method (repeating it gives the same result).
    

Example:

java
given()

  .when()

  .get(“https://api.example.com/users”)

  .then()

  .statusCode(200);

• Use case: Fetching a list of users.
  
• POST:
  
  • Sends data to the server to create a new resource.
    
  • It is not idempotent (repeating may create multiple entries).
    

Example:

java
given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 30 }”)

  .when()

  .post(“https://api.example.com/users”)

  .then()

  .statusCode(201);

• Use case: Creating a new user record.
  
• PUT:
  
  • Updates an existing resource or creates it if it doesn’t exist.
    
  • It is idempotent.
    

Example:

java

given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 31 }”)

  .when()

  .put(“https://api.example.com/users/1”)

  .then()

  .statusCode(200);

• Use case: Updating a user’s profile.
  
• DELETE:
  
  • Removes a resource from the server.
    

Example:

java
given()

  .when()

  .delete(“https://api.example.com/users/1”)

  .then()

  .statusCode(204);

• Use case: Deleting a user record.
  
• PATCH:
  
  • Partially updates a resource.
    
  • Only the specified fields are updated.
    

Example:

java
given()

  .contentType(“application/json”)

  .body(“{ \”age\”: 32 }”)

  .when()

  .patch(“https://api.example.com/users/1”)

  .then()

  .statusCode(200);

• Use case: Updating only the age of a user.
  

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2. What is the PUT method?

Answer:

The PUT method is mainly used to update an existing resource completely or create it if it doesn’t already exist.

• Idempotent Behavior:
  
  • Making the same PUT request multiple times produces the same result (no duplicate records).
    
• Common Use Case:
  
  • Updating the details of a user, such as name or age.
    

Example:

java
given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 30 }”)

  .when()

  .put(“https://api.example.com/users/1”)

  .then()

  .statusCode(200);

• • In this example, the user with ID 1 is updated with the provided details.
    
• Important Points:
  
  • If the resource does not exist, the server may create it (depending on API design).
    
  • PUT usually requires sending the full updated entity in the request body.
    

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3. What type of payload does POST support?

Answer:

The POST method supports sending various types of payloads to the server. Common formats include:

• JSON (JavaScript Object Notation):
  
  • Most widely used format for APIs.
    
  • Lightweight and easy to read.
    

Example:

java
given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 30 }”)

  .when()

  .post(“https://api.example.com/users”)

  .then()

  .statusCode(201);

• XML (Extensible Markup Language):
  
  • Used in older systems.
    
  • More verbose compared to JSON.
    

Example:

java
given()

  .contentType(“application/xml”)

  .body(“<user><name>John</name><age>30</age></user>”)

  .when()

  .post(“https://api.example.com/users”)

  .then()

  .statusCode(201);

• Form Data (application/x-www-form-urlencoded):
  
  • Used in web form submissions.
    

Example:

java
given()

  .contentType(“application/x-www-form-urlencoded”)

  .formParam(“name”, “John”)

  .formParam(“age”, “30”)

  .when()

  .post(“https://api.example.com/users”)

  .then()

  .statusCode(201);

• Multipart Data (multipart/form-data):
  
  • Used for file uploads.
    

Example:

java
given()

  .multiPart(new File(“/path/to/file”))

  .when()

  .post(“https://api.example.com/upload”)

  .then()

  .statusCode(201);

• Key Takeaway:
  
  • The server must know what content type is being sent, so setting the correct Content-Type header is very important.
    

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4. Key difference between PUT and POST

Answer:

Feature	PUT	POST
Purpose	Update existing resource or create if missing	Create a new resource
Idempotency	Idempotent (same result on multiple calls)	Not idempotent (creates new every time)
Payload Requirement	Requires full updated data	Can submit partial or full data
Example Usage	Update user profile	Register a new user

PUT Example:

java

given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 30 }”)

  .when()

  .put(“https://api.example.com/users/1”)

  .then()

  .statusCode(200);

POST Example:

java
given()

  .contentType(“application/json”)

  .body(“{ \”name\”: \”John\”, \”age\”: 30 }”)

  .when()

  .post(“https://api.example.com/users”)

  .then()

  .statusCode(201);

• Summary:
  
  • Use POST when creating a brand new resource.
    
  • Use PUT when updating an existing one or creating it at a specific URL if it doesn’t exist.
    

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5. Explain different data types in payload for API request

Answer:

APIs work with various types of data inside a payload (usually JSON or XML). These are the primary data types:

• String:
  
  • Represents a sequence of characters (text).
    

Example:

json
{ “name”: “John” }

• Number:
  
  • Can be integer or floating point.
    

Example:

json
{ “age”: 30 }

• Boolean:
  
  • Represents true or false values.
    

Example:

json
{ “isActive”: true }

• Array:
  
  • A list of values enclosed in square brackets.
    

Example:

json
{ “tags”: [“developer”, “blogger”] }

• Object:
  
  • A collection of key-value pairs (nested structures).
    

Example:

json

{

  “address”: {

    “street”: “123 Main St”,

    “city”: “Anytown”

  }

}

• Important Note:
  
  • Complex APIs often involve sending a mixture of these types inside the request payload.
    

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