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🔁 Using TestNG DataProvider for Parameterized API Testing

📘 Introduction​

Parameterized testing is a powerful technique that allows you to execute the same test logic with multiple sets of input data. TestNG's @DataProvider annotation simplifies this process by enabling you to pass different datasets to your tests dynamically. In this section, we’ll explore how to use @DataProvider effectively in RestAssured-based API tests.

🧠 1. What Is TestNG DataProvider?​

  • Definition: The @DataProvider annotation provides a way to supply multiple sets of input data to a single test method.

Key Features​

  • Supports complex datasets (e.g., arrays, objects)
  • Enables reuse of test logic
  • Helps test edge cases and invalid inputs

⚙️ 2. How to Use @DataProvider in RestAssured Tests​

Basic Example​

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

public class UserTests {

    @DataProvider(name = "userData")
    public Object[][] provideUserData() {
        return new Object[][] {
            { "John", "john@example.com" },
            { "Jane", "jane@example.com" },
            { "InvalidName", "invalid-email" }
        };
    }

    @Test(dataProvider = "userData")
    public void testCreateUser(String name, String email) {
        CreateUserRequest requestBody = new CreateUserRequest(name, email);

        given()
            .header("Content-Type", "application/json")
            .body(requestBody)
        .when()
            .post("/users")
        .then()
            .statusCode(201);
    }
}

Using External Data Sources​

@DataProvider(name = "externalUserData")
public Object[][] provideExternalUserData() throws Exception {
    ObjectMapper objectMapper = new ObjectMapper();
    List<UserData> userDataList = objectMapper.readValue(
        new File("src/test/resources/user-data.json"),
        new TypeReference<List<UserData>>() {}
    );

    Object[][] data = new Object[userDataList.size()][2];
    for (int i = 0; i < userDataList.size(); i++) {
        data[i][0] = userDataList.get(i).getName();
        data[i][1] = userDataList.get(i).getEmail();
    }
    return data;
}

✅ 3. Best Practices for Using @DataProvider​

  1. Keep data separate from code
  2. Include edge cases
  3. Log test data
System.out.println("Testing with name: " + name + ", email: " + email);
  1. Handle large datasets efficiently

🏁 Conclusion​

TestNG's @DataProvider is a powerful tool for implementing parameterized testing in RestAssured. It helps improve coverage and reusability of your API tests.