The micronaut-wiremock makes simple the use of WireMock for testing a Micronaut application.

To get started, add the following dependency to the project.

testImplementation "com.rapatao.micronaut:micronaut-wiremock:$version"

<dependency>
    <groupId>com.rapatao.micronaut</groupId>
    <artifactId>micronaut-wiremock</artifactId>
    <version>$version</version>
    <scope>test</scope>
</dependency>

By default, it will start the WireMockServer using port as 9090 and host as localhost. You can easily customize it using the project configuration file (application[-environment].yml).

wiremock:
    enabled: true
    port: 9090
    host: localhost

When a custom server is required by any reason, you can customize the WireMockServer providing a bean of type com.github.tomakehurst.wiremock.core.WireMockConfiguration. It's useful for testing scenarios which requires different types of extensions

IMPORTANT: The extension ResponseTemplateTransformer is globally active by default

The purpose of the library is simplifying the WireMockServer initialization, so, you can use all the usual methods provided by WireMock. If required, you can inject an instance of the WireMockServer and manipulate it directly.

import com.github.tomakehurst.wiremock.WireMockServer
import com.github.tomakehurst.wiremock.client.WireMock
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import jakarta.inject.Inject
import org.junit.jupiter.api.Test

@MicronautTest
internal class StubTest {

    @Inject
    lateinit var wireMockServer: WireMockServer

    @Test
    fun test() {
        wireMockServer.stubFor(WireMock.get("/").willReturn(WireMock.aResponse().withBody("ok")))
        ...
    }
}

import com.github.tomakehurst.wiremock.client.WireMock
import io.micronaut.test.extensions.junit5.annotation.MicronautTest
import org.junit.jupiter.api.Test

@MicronautTest
internal class Stub2Test {

    @Test
    fun test() {
        WireMock.stubFor(WireMock.get("/").willReturn(WireMock.aResponse().withBody("ok")))
        ...
    }
}

It is possible to move the stub creation from the testing block by using the JUnit 5 and the annotation @com.rapatao.micronaut.wiremock.junit.StubFor.

This annotation extends the JUnit, invoking a class to run the stub definition.

The @com.rapatao.micronaut.wiremock.junit.StubFor has an argument that must be used to define all com.rapatao.micronaut.wiremock.junit.StubDefinition that must be configured before the test execution. It accepts a list, that are invoked in the declared order.

class ExampleStubDefinition : StubDefinition {
    override fun configure() {
        WireMock.stubFor(
            ...
        )
        stubFor(
            ...
        )
    }
}

It is possible to declare the annotation in the class or in the method, each one works differently, as below:

When declared in a class, it acts as a @BeforeAll, invoking the stub definition class before all test methods, removing the identified mappings after all testes finish. When declared in a method, it acts as a @BeforeEach, invoking the stub definition class before each test method execution and remove the identified mappings after each execution.

The annotation, when declared at class level, must be after the @MicronautTest annotation. The JUnit invokes the extensions using the declared order, so, when the @StubFor is declared before the @MicronautTest, the Micronaut context is not yet initialized, which means, that the WireMock instance is not yet configured.