Error Handling and Logging

When testing APIs, it is important to:

Catch and manage errors gracefully.
Log details to understand what went wrong.

In this tutorial, you will learn:

Why Error Handling is Important
Handling API Errors with REST Assured
Logging Requests and Responses
Logging Errors for Debugging
Custom Error Messages
Using Try-Catch for Error Handling

Why Error Handling is Important

APIs can fail due to many reasons:

Invalid inputs (e.g., wrong data format)
Server issues (e.g., 500 Internal Server Error)
Authentication problems (e.g., 401 Unauthorized)
Resource not found (e.g., 404 Not Found)

Good error handling helps you:

Identify and fix problems faster.
Get clear error messages during test failures.
Ensure your tests are robust and reliable.

Handling API Errors with REST Assured

When calling an API, you must check for expected and unexpected responses.

Example: Handling a 404 Error (Resource Not Found)

Java

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given()
    .when()
    .get("http://192.xxx.xx.xxx:8080/books/20250401")
    .then()
    .statusCode(404)  // Check if resource is not found
    .body("error", equalTo("Book not found"));

Example: Handling 400 (Bad Request)

If the API expects specific data, sending the wrong input returns 400 Bad Request.

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given()
    .contentType("application/json")
    .body("{\"name\": \"\"}")  // Invalid input (empty name)
    .when()
    .post("https://api.example.com/users")
    .then()
    .statusCode(400)
    .body("message", containsString("Invalid name"));

Logging Requests and Responses

REST Assured provides built-in methods to log:

Requests (what you send)
Responses (what you receive)
Errors (in case of failures)

Log Everything (Request and Response)

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given()
    .log().all()  // Logs full request
    .when()
    .get("http://192.xxx.xx.xxx:8080/books/20250401")
    .then()
    .log().all()  // Logs full response
    .statusCode(200);

Log Only Errors

Logs only if the test fails.

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given()
    .log().ifValidationFails()  // Log only if there is a failure
    .when()
    .get("http://192.xxx.xx.xxx:8080/books/123")
    .then()
    .statusCode(200);  // This will fail and log the error

Log Request Details

Log only the request (helpful for debugging).

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given()
    .log().method()     // Log HTTP method (GET, POST, etc.)
    .log().uri()        // Log the request URL
    .log().headers()    // Log headers
    .log().body()       // Log request body (for POST/PUT)
    .when()
    .post("https://api.example.com/create");

Log Response Details

Log only the response.

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given()
    .when()
    .get("http://192.xxx.xx.xxx:8080/books/20250401")
    .then()
    .log().status()      // Logs status code (200, 404, etc.)
    .log().headers()     // Logs response headers
    .log().body();       // Logs the response body

Custom Error Messages

Add custom messages to make errors clearer.

Example: Custom Error Message

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given()
    .when()
    .get("http://192.xxx.xx.xxx:8080/books/20250401")
    .then()
    .statusCode(200)
    .body("name", equalTo("book 1"), "Name mismatch error!");

If the name does not match, you'll see:

java.lang.AssertionError: Name mismatch error!

Using Try-Catch for Error Handling

You can wrap your API calls in a try-catch block to handle exceptions.

Example: Handling Exceptions Gracefully

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try {
    Response response = 
        given()
            .when()
            .get("http://192.xxx.xx.xxx:8080/books/20250401");
    
    if (response.statusCode() != 200) {
        System.out.println("Error: Unexpected Status Code " + response.statusCode());
    } else {
        System.out.println("Success: " + response.asString());
    }

} catch (Exception e) {
    System.out.println("Exception occurred: " + e.getMessage());
}

Example: Retry on Failure

If an API is unstable, you may retry it.

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int retries = 3;
boolean success = false;

for (int i = 0; i < retries; i++) {
    try {
        given()
            .when()
            .get("https://api.example.com/status")
            .then()
            .statusCode(200);
        success = true;
        break;  // Exit loop if successful
    } catch (Exception e) {
        System.out.println("Retrying... Attempt: " + (i + 1));
    }
}

if (!success) {
    throw new RuntimeException("API failed after " + retries + " retries");
}

Handling JSON Parsing Errors

If the response is not in the expected format, it can cause parsing errors.

Example: Safely Parse JSON

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try {
    Response response = given()
        .when()
        .get("https://api.example.com/data");

    String value = response.jsonPath().getString("nonExistingField");
    System.out.println("Value: " + value);
    
} catch (Exception e) {
    System.out.println("Parsing Error: " + e.getMessage());
}

Validating Response Time

Ensure the API responds within a specific time.

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given()
    .when()
    .get("https://api.example.com/health")
    .then()
    .time(lessThan(3000L));  // Response must be under 3 seconds