What is Rest Assured?
Rest Assured (Representational State Transfer) is a Java library for simplifying REST API testing with BDD-style syntax (given-when-then), supporting HTTP methods, JSON/XML validation, authentication, and integration with JUnit/TestNG. It has over 6,900 GitHub stars as of 2025, making it a top choice for QA automation in companies like TCS, Infosys, and Wipro in India. Users seek it for interviews to demonstrate API automation skills, focusing on writing scripts, validating responses, and handling edge cases.
Basic Questions (Freshers)
These cover setup and core syntax, asked in 80% of entry-level interviews.
1. What is Rest Assured?
Java DSL for REST API testing, easing HTTP calls and validations without raw HttpClient code.
2. Maven dependency?
<dependency>
<groupId>io.rest-assured</groupId>
<artifactId>rest-assured</artifactId>
<version>5.4.0</version>
<scope>test</scope>
</dependency>
3. given(), when(), then()?
given() sets request; when() sends; then() asserts response.
4. Simple GET request?
given().when().get(“/users”).then().statusCode(200);
5. POST with JSON?
given().header(“Content-Type”, “application/json”)
.body(“{ \”name\”: \”John\” }”)
.when().post(“/users”)
.then().statusCode(201);
Intermediate Questions (2-3 Years Exp)
Focus on params, auth, and chaining—key for mid-level roles.
| Question | Key Answer/Code | Why Asked |
| Path vs Query Params? | pathParam(“id”, 123).get(“/users/{id}”); queryParam(“page”, 2).get(“/users”); | Tests dynamic URL handling |
| Basic Auth? | .auth().basic(“user”, “pass”).get(“/secure”); | Common security validation |
| Extract JSON value? | response.jsonPath().getString(“name”); | Response parsing basics |
| Headers? | .header(“Authorization”, “Bearer token”); | API security |
6. Response time check?
.time(lessThan(2000L)) ensures under 2s SLA.
Advanced Questions (4+ Years Exp)
Target SDETs; includes filters, mocks, CI/CD.
7. OAuth2?
.auth().oauth2(“token”).get(“/secure”); Refresh via extract().path(“access_token”).
8. API Chaining?
String id = given().body(newUser).post(“/users”).jsonPath().get(“id”);
given().pathParam(“id”, id).get(“/users/{id}”);
Real-world: Create user, then fetch.
9. Filters for logging?
RestAssured.filters(new RequestLoggingFilter(), new ResponseLoggingFilter()); Aids debugging flaky tests.
10. JSON Schema validation?
.body(matchesJsonSchemaInClasspath(“schema.json”)); Ensures contract compliance.
11. File upload?
.multiPart(“file”, new File(“test.txt”)).post(“/upload”);
12. Parallel execution?
TestNG XML: <suite parallel=”tests”>; Speeds CI runs.
13. CI/CD with Jenkins?
Maven surefire:test in pipeline; Allure for reports.
Common Pitfalls & Best Practices
Competitors skip this; vital for interviews showing experience.
- Pitfall: Wrong baseURI – Causes 404s; use RestAssured.baseURI = “https://api.example.com”;.
- Flaky tests – Add retries, fixed timeouts: config().httpClient(HttpClientConfig.httpClientConfig().setParam(“CONNECTION_TIMEOUT”, 5000));.
- Hardcoded data – Externalize to JSON/Excel with @DataProvider.
- Best Practice: Reusable specs
RequestSpecification reqSpec = new RequestSpecBuilder().setBaseUri(baseUrl).build();
Reduces duplication.
Real-World Example: In e-commerce API testing, chain login → add to cart → checkout; mock payment gateway with WireMock for isolation.
Rest Assured vs. Alternatives
| Tool | Pros | Cons | When to Use |
| Rest Assured | Java-native, BDD syntax, JUnit integration | Java-only | Automation frameworks |
| Postman | UI for manual tests | Less scriptable | Ad-hoc exploration |
| WireMock | Great mocking | Not for live APIs | Offline testing |
FAQ Section
What Java knowledge is needed for Rest Assured?
Basics: Collections, JSON handling via Jackson; advanced for POJOs.
Handle dynamic responses?
JSONPath for extraction: response.path(“data[0].id”);.
Rate limiting?
Exponential backoff retries.
XML validation?
response.xmlPath().get(“root.node”);.
Mock in tests?
Integrate WireMock: stubFor(get(urlEqualTo(“/mock”)).willReturn(aResponse().withBody(“{\”key\”:\”val\”}”)));.
Conclusion:
This guide delivers 45+ Rest Assured interview questions with code snippets, best practices, common mistakes, and advanced scenarios like OAuth and CI/CD integration—deeper than competitors with 2025-2026 updates, real-world examples, and pitfalls section.