What is POST API?
A POST API is an API endpoint that allows clients to send data to a server so that the server can process it and often create a new resource. Unlike a GET API, which is only used to retrieve data, a POST API typically involves submitting information such as form data, JSON payloads, or file uploads. For example, creating a new user account, submitting a login form, or uploading a file are common use cases of POST APIs.
How to Test a POST API with Playwright Java
Playwright is primarily a UI automation tool, but it also provides ways to send API requests directly without interacting with the browser. In Java, you can use Playwright’s APIRequestContext to test POST APIs. The high-level steps are:
Create an APIRequestContext
- Initialize a Playwright request context that acts as a client for making API calls.
- This context allows you to set a base URL, headers, or authentication details.
Prepare the POST Request
- Define the API endpoint you want to test.
- Construct the body of the request, which might include JSON, form-data, or raw text.
- Attach required headers such as Content-Type: application/json or authorization tokens if needed.
Send the POST Request
- Use the context to send the POST request along with the payload.
- The server processes the request and returns a response.
Validate the Response
- Check the status code (e.g., 200 for success, 201 for resource created, 400 for bad request).
- Validate the response body to ensure that the server returned the correct data or confirmation.
- Verify response headers if necessary.
Assertions in TestNG/JUnit
- In actual testing, you would assert expected vs. actual values.
- For example, if you created a new user, you’d assert that the response contains the user ID or success message.
Integration with UI Tests (Optional)
- Sometimes you may chain API and UI testing.
- For example: Use the POST API to create a user. Then, log in with that user in the UI using Playwright’s browser automation.
Steps to Test a POST API using Playwright Java:
- Initialize Playwright and create an APIRequestContext.
- Use
post()method to send a POST request. - Pass headers, payload (body), and endpoint URL.
- Read and validate the response (status code, body, etc.).
- Close the context.
Example: POST API Test in Playwright Java
Let’s take an example of a fake JSON placeholder API:
Endpoint: https://jsonplaceholder.typicode.com/posts
Method: POST
Payload:
{ "title": "foo", "body": "bar", "userId": 1 }
import com.microsoft.playwright.*; import java.util.*; public class PostApiTest { public static void main(String[] args) { try (Playwright playwright = Playwright.create()) { // Create APIRequestContext APIRequest apiRequest = playwright.request(); APIRequestContext requestContext = apiRequest.newContext(); // Define the payload Map<String, Object> payload = new HashMap<>(); payload.put("title", "foo"); payload.put("body", "bar"); payload.put("userId", 1); // Send POST request APIResponse response = requestContext.post("https://jsonplaceholder.typicode.com/posts", RequestOptions.create() .setHeader("Content-Type", "application/json") .setData(payload) ); // Validate response System.out.println("Status Code: " + response.status()); System.out.println("Response Body: " + response.text()); if (response.status() == 201) { System.out.println("POST API test passed!"); } else { System.out.println("POST API test failed!"); } // Close context requestContext.dispose(); } } }
Status Code: 201 Response Body: { "title": "foo", "body": "bar", "userId": 1, "id": 101 } POST API test passed!
Above is the output, having status code 201 as this is POST request and response body is JSON object which can be validate by JSONObject class
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