Q18 of 40 · REST Assured

How would you integrate REST Assured tests with TestNG vs JUnit 5? What changes?

REST AssuredMidrest-assuredjunit5testngintegrationparallel-testing

Short answer

Short answer: With JUnit 5, use @BeforeAll/@Test from org.junit.jupiter.api — no REST Assured config needed. TestNG uses @BeforeClass/@Test from org.testng. The main difference is parallel execution config: JUnit 5 uses junit-platform.properties; TestNG uses the XML suite file with parallel and thread-count attributes.

Detail

REST Assured is framework-agnostic — it is just a library, so the only difference is the test lifecycle annotations and how you configure parallelism.

JUnit 5 setup:

@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
class UserApiTest extends BaseApiTest {
    @BeforeAll static void init() { /* build specs */ }
    @Test void getUser_returnsUser() { ... }
}

Parallel execution via junit-platform.properties:

junit.jupiter.execution.parallel.enabled = true
junit.jupiter.execution.parallel.mode.default = concurrent
junit.jupiter.execution.parallel.config.strategy = fixed
junit.jupiter.execution.parallel.config.fixed.parallelism = 4

TestNG setup:

public class UserApiTest extends BaseApiTest {
    @BeforeClass public void init() { /* build specs */ }
    @Test public void getUser_returnsUser() { ... }
}

Parallel execution in testng.xml:

<suite name="API Suite" parallel="methods" thread-count="4">

Key risk for both: REST Assured is thread-safe when you use local RequestSpecification instances. Static RestAssured.* fields (baseURI, port) are shared — use given(localSpec) rather than the static defaults when running parallel tests.

// EXAMPLE

BaseApiTest.java

// JUnit 5 version
@ExtendWith(SoftAssertionsExtension.class)
public abstract class BaseApiTestJUnit5 {
    protected static RequestSpecification reqSpec;
    protected static ResponseSpecification resSpec;

    @BeforeAll
    static void buildSpecs() {
        reqSpec = new RequestSpecBuilder()
            .setBaseUri(System.getenv("API_BASE_URL"))
            .addHeader("Authorization", "Bearer " + getToken())
            .setContentType(ContentType.JSON)
            .build();
        resSpec = new ResponseSpecBuilder()
            .expectContentType(ContentType.JSON)
            .build();
    }
}

// TestNG version — same content, different annotations
public abstract class BaseApiTestTestNG {
    protected static RequestSpecification reqSpec;

    @BeforeClass
    public void buildSpecs() {          // note: not static in TestNG
        reqSpec = new RequestSpecBuilder()
            .setBaseUri(System.getenv("API_BASE_URL"))
            .addHeader("Authorization", "Bearer " + getToken())
            .build();
    }
}

// WHAT INTERVIEWERS LOOK FOR

Correct annotation packages (junit.jupiter vs testng), understanding that REST Assured itself requires no configuration change, and the crucial parallel safety requirement of using local specs over static fields.

// COMMON PITFALL

Mixing JUnit 4 (@Before, @BeforeClass) annotations with JUnit 5 — they are silently ignored by JUnit 5's engine, so setup never runs and every test fails with a NullPointerException on the spec.

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