How to Test a POST API by Rest Assured

 

To test a POST API using Rest Assured with a JSONObject in Java, follow these steps:

Step-by-Step Implementation

1. Add Rest Assured Dependency

<dependencies>
    <!-- Rest Assured -->
    <dependency>
        <groupId>io.rest-assured</groupId>
        <artifactId>rest-assured</artifactId>
        <version>5.3.0</version>
        <scope>test</scope>
    </dependency>

    <!-- JSON Library -->
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20230618</version>
    </dependency>
</dependencies>

API to be tested: 

POST https://reqres.in/api/users

Sample request body:

{
  "name": "Himanshu",
  "job": "QA Engineer"
}

Expected response (201 Created):

{
  "name": "Himanshu",
  "job": "QA Engineer",
  "id": "123",
  "createdAt": "2025-07-28T..."
}

3. Java Code to Test POST API using JSONObject

import io.restassured.RestAssured;
import io.restassured.response.Response;
import io.restassured.http.ContentType;
import org.json.JSONObject;

public class PostAPITest {

    public static void main(String[] args) {

        // Step 1: Set Base URI
        RestAssured.baseURI = "https://reqres.in/api";

        // Step 2: Create Request Payload using JSONObject
        JSONObject requestBody = new JSONObject();
        requestBody.put("name", "Himanshu");
        requestBody.put("job", "QA Engineer");

        // Step 3: Make POST Request
        Response response = RestAssured
            .given()
                .contentType(ContentType.JSON)
                .body(requestBody.toString())
                .log().all()
            .when()
                .post("/users")
            .then()
                .log().all()
                .statusCode(201)
                .extract().response();

        // Step 4: Print Response Fields
        System.out.println("ID: " + response.jsonPath().getString("id"));
        System.out.println("Created At: " + response.jsonPath().getString("createdAt"));
    }
}

Code Explanation:

Line	Purpose
RestAssured.baseURI	Sets the base URL.
JSONObject	Builds the JSON body using key-value pairs.
given().contentType().body()	Prepares the request with headers and body.
post("/users")	Sends POST request to the endpoint.
statusCode(201)	Verifies the response status.
response.jsonPath()	Extracts values from JSON response.

Sample Output:

Request method:	POST
Request URI:	https://reqres.in/api/users
Request body:
{
    "name": "Himanshu",
    "job": "QA Engineer"
}
Response Status Code: 201
Response body:
{
    "name": "Himanshu",
    "job": "QA Engineer",
    "id": "867",
    "createdAt": "2025-07-28T14:30:55.098Z"
}