Subject:

IndexOutOfBoundsException

in WireMock during Test Setup Message: Hi WireMock team, I’m encountering an issue when running tests with WireMock in my Java project. The error occurs during the initialization of the

WireMockExtension

in my test class:

java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
    at java.base/java.util.Objects.checkIndex(Objects.java:385)
    at java.base/java.util.ArrayList.get(ArrayList.java:427)
    at com.github.tomakehurst.wiremock.http.HttpServerFactoryLoader.pickMostAppropriateFrom(HttpServerFactoryLoader.java:77)
    at com.github.tomakehurst.wiremock.http.HttpServerFactoryLoader.load(HttpServerFactoryLoader.java:57)
    at com.github.tomakehurst.wiremock.WireMockServer.getHttpServerFactory(WireMockServer.java:89)
    at com.github.tomakehurst.wiremock.WireMockServer.<init>(WireMockServer.java:72)
    at com.github.tomakehurst.wiremock.junit5.WireMockExtension.startServerIfRequired(WireMockExtension.java:215)
    at com.github.tomakehurst.wiremock.junit5.WireMockExtension.beforeAll(WireMockExtension.java:282)

Here’s the relevant part of my test setup:

@ExtendWith(WireMockExtension.class)
@SpringBootTest
public class WeatherControllerTest {

    private final RestTemplate restTemplate = new RestTemplate();

    @Test
    public void testAddWeather() {
        stubFor(post(urlEqualTo("/api/weather"))
            .willReturn(aResponse()
                .withStatus(201)
                .withBody("Weather data added successfully.")));

        String url = "<http://localhost:8080/api/weather>";
        String payload = "{ \"location\": { \"cityName\": \"New York\" }, \"condition\": { \"temperature\": 22.5 }, \"timestamp\": \"2025-01-01T10:00:00\" }";

        ResponseEntity<String> response = restTemplate.postForEntity(url, payload, String.class);

        assertEquals(HttpStatus.CREATED, response.getStatusCode());
        assertEquals("Weather data added successfully.", response.getBody());

        verify(postRequestedFor(urlEqualTo("/api/weather")));
    }
}

Steps I’ve Tried: 1. Ensured that WireMock is included in my `pom.xml`:

<dependency>
            <groupId>org.wiremock</groupId>
            <artifactId>wiremock</artifactId>
            <version>3.10.0</version>
            <scope>test</scope>
        </dependency>

2. Cleaned and rebuilt the project. Has anyone encountered this issue before? Is there a missing dependency or configuration I need to include? Any help would be appreciated. Thanks in advance!

I had a similar issue, I think it was because of a conflict on the jetty versions. I fixed it by using the spring-boot integration: https://wiremock.org/docs/spring-boot/ https://github.com/wiremock/wiremock-spring-boot

Thanks. I got rid of

@ExtendWith(WireMockExtension.class)

and manually initialized the

WireMockServer

in my

@BeforeEach

method. This approach worked perfectly.

When you use the Spring Boot integration, you can use @EnableWireMock at the class level. It is quite neat and works nicely. In case you can't do that, you can still use the Spring Boot integration but with an explicit WireMock instantiation. I wrote a tutorial: https://medium.com/@arc-e-tect/wiremock-cucumber-and-springboot-ae3e107bd3d7