WireMock Basics

WireMock is a simulator for HTTP-based APIs. It is often used for testing applications that rely on external APIs by mocking the API responses. WireMock can be used as a standalone server or as a library within your Java project.

Key Features

• HTTP Response Stubbing: Define expected HTTP responses for specific requests.
• Request Verification: Verify that specific requests were made.
• Proxying: Forward requests to other services and capture responses.
• Record & Playback: Record real API interactions and replay them later.
• Dynamic Response Generation: Generate responses dynamically based on request parameters.
• Simulate Faults: Simulate network delays, timeouts, and other faults.

Getting Started

Installation

You can use WireMock in two ways:

1. Standalone Server:

   • Download the standalone JAR from the official WireMock website.
   • Run the server using the following command:

     java -jar wiremock-standalone-2.27.2.jar --port 8080
   • This will start WireMock on port 8080.

2. Java Library:

   • Add WireMock as a dependency in your pom.xml (for Maven) or build.gradle (for Gradle).
   • Maven:

     <dependency>
         <groupId>com.github.tomakehurst</groupId>
         <artifactId>wiremock</artifactId>
         <version>2.27.2</version>
         <scope>test</scope>
     </dependency>
   • Gradle:

     testImplementation 'com.github.tomakehurst:wiremock:2.27.2'

Basic Usage

Stubbing Responses

You can define stubs to mock API responses. Here’s an example of how to stub a GET request:

import com.github.tomakehurst.wiremock.client.WireMock;

public class WireMockExample {
    public static void main(String[] args) {
        WireMock.configureFor("localhost", 8080);
        WireMock.stubFor(WireMock.get(WireMock.urlEqualTo("/api/resource"))
            .willReturn(WireMock.aResponse()
                .withStatus(200)
                .withBody("{\"message\": \"Hello, World!\"}")));
    }
}

Verifying Requests

You can verify that a specific request was made:

WireMock.verify(WireMock.getRequestedFor(WireMock.urlEqualTo("/api/resource")));

Proxying Requests

You can verify that a specific request was made:

WireMock.stubFor(WireMock.get(WireMock.urlMatching(".*"))
    .willReturn(WireMock.aResponse().proxiedFrom("https://www.confusedtester.com")));

Advanced Features

• Dynamic Templating: Use Handlebars templates to generate dynamic responses.
• Fault Injection: Simulate network issues by injecting delays or returning error responses.
• Recording: Record real API interactions and save them as stubs for later use.

Example: Simulating a Delay

WireMock.stubFor(WireMock.get(WireMock.urlEqualTo("/api/resource"))
    .willReturn(WireMock.aResponse()
        .withStatus(200)
        .withBody("{\"message\": \"Hello, Mr B.!\"}")
        .withFixedDelay(5000))); // 5-second delay

Conclusion

WireMock is a powerful tool for testing and simulating HTTP-based APIs. Whether you're running it as a standalone server or embedding it in your Java project, WireMock provides a flexible and easy-to-use solution for mocking API responses, verifying requests, and simulating various network conditions.

For more detailed documentation, visit the official WireMock documentation..