REST Assured Java Tutorial: Complete 2026 Guide

Last updated: June 27, 2026 · 9 min read

REST Assured is the most popular Java library for API testing in 2026. This tutorial takes you from setup to production-ready API test suites in 60 minutes. Pair it with our API Testing Tutorial, Postman API Testing, and RestSharp C# Tutorial.

REST Assured is a Java DSL (Domain Specific Language) for testing REST APIs. It provides a fluent, BDD-style syntax that makes API tests readable and maintainable. The library is documented at rest-assured.io.

given()
    .baseUri("https://api.example.com")
.when()
    .get("/users/1")
.then()
    .statusCode(200)
    .body("name", equalTo("Leanne Graham"));

• Java 17 LTS or 21 LTS
• Maven 3.9+ or Gradle 8+
• IDE — IntelliJ IDEA recommended

Maven (pom.xml)

<dependencies>
    <dependency>
        <groupId>io.rest-assured</groupId>
        <artifactId>rest-assured</artifactId>
        <version>5.5.0</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter</artifactId>
        <version>5.10.3</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Gradle (build.gradle)

dependencies {
    testImplementation 'io.rest-assured:rest-assured:5.5.0'
    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.3'
}

import static io.restassured.RestAssured.*;
import static org.hamcrest.Matchers.*;
import org.junit.jupiter.api.Test;

public class FirstApiTest {

    @Test
    void getUserById() {
        given()
            .baseUri("https://jsonplaceholder.typicode.com")
        .when()
            .get("/users/{id}", 1)
        .then()
            .statusCode(200)
            .body("id", equalTo(1))
            .body("email", matchesPattern(".*@.*"))
            .time(lessThan(2000L));
    }
}

Run with mvn test.

@Test
void createUser() {
    given()
        .baseUri("https://api.example.com")
        .contentType("application/json")
        .body("""
            {
              "name": "Alice Johnson",
              "email": "alice@example.com",
              "role": "admin"
            }
            """)
    .when()
        .post("/users")
    .then()
        .statusCode(201)
        .body("id", notNullValue())
        .body("email", equalTo("alice@example.com"));
}

@Test
void updateUser() {
    given()
        .baseUri("https://api.example.com")
        .contentType("application/json")
        .body("{ \"name\": \"Alice Updated\" }")
    .when()
        .put("/users/1")
    .then()
        .statusCode(200)
        .body("name", equalTo("Alice Updated"));
}

@Test
void deleteUser() {
    when()
        .delete("/users/1")
    .then()
        .statusCode(204);
}

Bearer Token

String token = given()
    .body("{ \"email\": \"admin@example.com\", \"password\": \"Sup3rSecret!\" }")
    .contentType("application/json")
.when()
    .post("/auth/login")
.then()
    .extract().path("token");

given()
    .auth().oauth2(token)
.when()
    .get("/admin/users")
.then()
    .statusCode(200);

Basic Auth

given()
    .auth().basic("admin", "Sup3rSecret!")
.when()
    .get("/admin/dashboard")
.then()
    .statusCode(200);

given()
    .get("/users/1")
.then()
    .body("address.city", equalTo("Gwenborough"))
    .body("company.name", startsWith("Romaguera"))
    .body("id", greaterThan(0))
    .body("email", containsString("@"));

Add the networknt validator:

<dependency>
    <groupId>com.networknt</groupId>
    <artifactId>json-schema-validator</artifactId>
    <version>1.4.0</version>
    <scope>test</scope>
</dependency>

@Test
void validateAgainstSchema() {
    InputStream schemaStream = getClass().getResourceAsStream("/schemas/user.json");

    given()
        .get("/users/1")
    .then()
        .body(matchesJsonSchema(schemaStream));
}

public class ApiSpecs {
    public static RequestSpecification authSpec() {
        return new RequestSpecBuilder()
            .setBaseUri("https://api.example.com")
            .setContentType("application/json")
            .addHeader("X-API-Version", "v1")
            .build();
    }

    public static ResponseSpecification successResponse() {
        return new ResponseSpecBuilder()
            .expectStatusCode(200)
            .expectContentType("application/json")
            .build();
    }
}

@Test
void testWithSpec() {
    given()
        .spec(ApiSpecs.authSpec())
        .body("{ \"name\": \"Alice\" }")
    .when()
        .post("/users")
    .then()
        .statusCode(201);
}

Data-driven testing

@ParameterizedTest
@CsvSource({
    "admin@example.com, Sup3rSecret!",
    "viewer@example.com, ViewerPass1!"
})
void loginTest(String email, String password) {
    given()
        .body(Map.of("email", email, "password", password))
    .when()
        .post("/auth/login")
    .then()
        .statusCode(200);
}

Extract and chain

String userId = given()
    .body(createUserPayload)
    .post("/users")
.then()
    .extract().path("id");

given()
    .pathParam("id", userId)
.when()
    .get("/users/{id}")
.then()
    .statusCode(200)
    .body("id", equalTo(userId));

File upload

given()
    .multiPart("file", new File("/path/to/file.pdf"))
    .post("/upload")
.then()
    .statusCode(200);

Mocking with WireMock

WireMockServer wireMock = new WireMockServer(8080);
wireMock.stubFor(get(urlEqualTo("/api/users"))
    .willReturn(aResponse().withBody("{ \"id\": 1 }")));

name: REST Assured Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-java@v4
        with: { distribution: temurin, java-version: '17' }
      - run: mvn -B test

For broader CI patterns, see our GitHub Actions CI guide.

Do

• Use specs for shared configuration and auth tokens
• Validate JSON schemas on every test
• Run in CI on every PR
• Use JUnit 5 or TestNG for organization

Don't

• Don't hardcode URLs or tokens
• Don't skip schema validation
• Don't share state across tests
• Don't use REST Assured for UI testing (it's API only)

• API Testing Ultimate Guide
• Postman API Testing Tutorial
• RestSharp C# API Automation
• GraphQL API Testing
• API Testing Interview Questions
• SDET Career Roadmap