# REST Assured — Fluent Java API Testing for RESTful Services

> REST Assured is a Java library for testing REST APIs with a fluent, BDD-style syntax. It simplifies HTTP request construction, response validation, and JSON/XML assertion, making API tests readable and concise in Java and Kotlin projects.

## Install

Save as a script file and run:

# REST Assured — Fluent Java API Testing for RESTful Services

## Quick Use
```xml
<!-- Maven dependency -->
<dependency>
    <groupId>io.rest-assured</groupId>
    <artifactId>rest-assured</artifactId>
    <version>5.5.0</version>
    <scope>test</scope>
</dependency>
```
```java
import static io.restassured.RestAssured.*;
import static org.hamcrest.Matchers.*;

given().
    queryParam("page", 1).
when().
    get("/api/users").
then().
    statusCode(200).
    body("data.size()", greaterThan(0));
```

## Introduction
REST Assured is a Java DSL for simplifying the testing of REST-based APIs. It brings the ease of dynamic-language HTTP testing to Java by providing a fluent given/when/then syntax for constructing requests and validating responses. It is widely used in enterprise Java projects for both unit and integration API testing.

## What REST Assured Does
- Sends HTTP requests (GET, POST, PUT, DELETE, PATCH) with a readable fluent API
- Validates response status codes, headers, cookies, and body content in a single chain
- Parses and asserts JSON and XML response bodies using GPath and JsonPath expressions
- Supports authentication schemes including Basic, Digest, OAuth 1/2, and custom headers
- Integrates with JUnit, TestNG, and assertion libraries like Hamcrest and AssertJ

## Architecture Overview
REST Assured wraps Apache HttpClient to handle HTTP communication and provides a specification builder that accumulates request parameters (headers, query params, body, auth) through method chaining. The response object exposes a rich API for extracting and asserting values. JSON validation uses Groovy's GPath syntax via an embedded JsonPath engine, while XML uses XmlPath. The library ships as a single jar with optional modules for JSON Schema validation, Kotlin extensions, and Spring MockMvc integration.

## Self-Hosting & Configuration
- Add the Maven or Gradle dependency to your test scope
- Set a base URI globally with `RestAssured.baseURI = "http://localhost:8080"` in a setup method
- Configure default headers, authentication, and content type via `RestAssured.config`
- Use request and response specifications to avoid repeating common setup across tests
- Enable logging with `.log().all()` on requests or responses for debugging

## Key Features
- BDD-style given/when/then syntax for readable and self-documenting API tests
- JsonPath and XmlPath for deep assertions on nested response structures
- JSON Schema validation to verify response structure matches a contract
- Spring MockMvc integration for testing Spring Boot controllers without a running server
- Kotlin extensions module for even more idiomatic test code

## Comparison with Similar Tools
- **HTTPie / curl** — command-line tools for manual testing; not integrated into test suites
- **Postman / Newman** — GUI-first API testing with collection runners; less natural for Java CI pipelines
- **Spring WebTestClient** — reactive testing client for Spring WebFlux; Spring-specific
- **Karate** — BDD API testing with its own DSL in feature files; less Java-native
- **WireMock** — API mocking and stubbing; complementary to REST Assured for service virtualization

## FAQ
**Q: Can I use REST Assured with Kotlin?**
A: Yes. There is a dedicated Kotlin extensions module that provides infix functions for even cleaner syntax.

**Q: Does it support multipart file uploads?**
A: Yes. Use `.multiPart(file)` in the request specification to upload files.

**Q: How do I validate JSON Schema?**
A: Add the `rest-assured-json-schema-validator` module and use `.body(matchesJsonSchemaInClasspath("schema.json"))`.

**Q: Can I test SOAP or GraphQL APIs?**
A: REST Assured is designed for REST APIs but can send arbitrary HTTP requests, so GraphQL queries via POST work fine. For SOAP, dedicated libraries like Apache CXF are better suited.

## Sources
- https://github.com/rest-assured/rest-assured
- https://rest-assured.io/


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Source: https://tokrepo.com/en/workflows/asset-8ad83f90
Author: Script Depot