Write tests with WireMock and Testcontainers

Table of contents

Mocking external API interactions at the HTTP protocol level, rather than mocking Java methods, lets you verify marshalling and unmarshalling behavior and simulate network issues.

Test using WireMock JUnit 5 extension

WireMock provides a JUnit 5 extension that starts an in-process WireMock server. You can configure stub responses using the WireMock Java API.

Create AlbumControllerTest.java:

package com.testcontainers.demo;

import static com.github.tomakehurst.wiremock.client.WireMock.aResponse;
import static com.github.tomakehurst.wiremock.client.WireMock.urlMatching;
import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.Matchers.hasSize;
import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;

import com.github.tomakehurst.wiremock.client.WireMock;
import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
import io.restassured.RestAssured;
import io.restassured.http.ContentType;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.RegisterExtension;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.http.MediaType;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;

@SpringBootTest(webEnvironment = RANDOM_PORT)
class AlbumControllerTest {

  @LocalServerPort
  private Integer port;

  @RegisterExtension
  static WireMockExtension wireMock = WireMockExtension
    .newInstance()
    .options(wireMockConfig().dynamicPort())
    .build();

  @DynamicPropertySource
  static void configureProperties(DynamicPropertyRegistry registry) {
    registry.add("photos.api.base-url", wireMock::baseUrl);
  }

  @BeforeEach
  void setUp() {
    RestAssured.port = port;
  }

  @Test
  void shouldGetAlbumById() {
    Long albumId = 1L;

    wireMock.stubFor(
      WireMock
        .get(urlMatching("/albums/" + albumId + "/photos"))
        .willReturn(
          aResponse()
            .withHeader("Content-Type", MediaType.APPLICATION_JSON_VALUE)
            .withBody(
              """
              [
                   {
                       "id": 1,
                       "title": "accusamus beatae ad facilis cum similique qui sunt",
                       "url": "https://via.placeholder.com/600/92c952",
                       "thumbnailUrl": "https://via.placeholder.com/150/92c952"
                   },
                   {
                       "id": 2,
                       "title": "reprehenderit est deserunt velit ipsam",
                       "url": "https://via.placeholder.com/600/771796",
                       "thumbnailUrl": "https://via.placeholder.com/150/771796"
                   }
               ]
              """
            )
        )
    );

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(200)
      .body("albumId", is(albumId.intValue()))
      .body("photos", hasSize(2));
  }

  @Test
  void shouldReturnServerErrorWhenPhotoServiceCallFailed() {
    Long albumId = 2L;
    wireMock.stubFor(
      WireMock
        .get(urlMatching("/albums/" + albumId + "/photos"))
        .willReturn(aResponse().withStatus(500))
    );

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(500);
  }
}

Here's what the test does:

@SpringBootTest starts the full application on a random port.
@RegisterExtension creates a WireMockExtension that starts WireMock on a dynamic port.
@DynamicPropertySource overrides photos.api.base-url to point at the WireMock endpoint, so the application talks to WireMock instead of the real photo service.
shouldGetAlbumById() configures a stub response for /albums/{albumId}/photos, sends a request to the application's /api/albums/{albumId} endpoint, and verifies the response body.
shouldReturnServerErrorWhenPhotoServiceCallFailed() configures WireMock to return a 500 status and verifies that the application propagates that status to the caller.

Stub using JSON mapping files

Instead of using the WireMock Java API, you can configure stubs with JSON mapping files. Create src/test/resources/wiremock/mappings/get-album-photos.json:

{
  "mappings": [
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/([0-9]+)/photos"
      },
      "response": {
        "status": 200,
        "headers": {
          "Content-Type": "application/json"
        },
        "bodyFileName": "album-photos-resp-200.json"
      }
    },
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/2/photos"
      },
      "response": {
        "status": 500,
        "headers": {
          "Content-Type": "application/json"
        }
      }
    },
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/3/photos"
      },
      "response": {
        "status": 200,
        "headers": {
          "Content-Type": "application/json"
        },
        "jsonBody": []
      }
    }
  ]
}

Create the response body file at src/test/resources/wiremock/__files/album-photos-resp-200.json:

[
  {
    "id": 1,
    "title": "accusamus beatae ad facilis cum similique qui sunt",
    "url": "https://via.placeholder.com/600/92c952",
    "thumbnailUrl": "https://via.placeholder.com/150/92c952"
  },
  {
    "id": 2,
    "title": "reprehenderit est deserunt velit ipsam",
    "url": "https://via.placeholder.com/600/771796",
    "thumbnailUrl": "https://via.placeholder.com/150/771796"
  }
]

Initialize WireMock to load stubs from the mapping files:

@RegisterExtension
static WireMockExtension wireMockServer = WireMockExtension
  .newInstance()
  .options(
    wireMockConfig().dynamicPort().usingFilesUnderClasspath("wiremock")
  )
  .build();

With mapping-based stubs in place, create AlbumControllerWireMockMappingTests.java:

package com.testcontainers.demo;

import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.Matchers.hasSize;
import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;

import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
import io.restassured.RestAssured;
import io.restassured.http.ContentType;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.RegisterExtension;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;

@SpringBootTest(webEnvironment = RANDOM_PORT)
class AlbumControllerWireMockMappingTests {

  @LocalServerPort
  private Integer port;

  @RegisterExtension
  static WireMockExtension wireMockServer = WireMockExtension
    .newInstance()
    .options(
      wireMockConfig().dynamicPort().usingFilesUnderClasspath("wiremock")
    )
    .build();

  @DynamicPropertySource
  static void configureProperties(DynamicPropertyRegistry registry) {
    registry.add("photos.api.base-url", wireMockServer::baseUrl);
  }

  @BeforeEach
  void setUp() {
    RestAssured.port = port;
  }

  @Test
  void shouldGetAlbumById() {
    Long albumId = 1L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(200)
      .body("albumId", is(albumId.intValue()))
      .body("photos", hasSize(2));
  }

  @Test
  void shouldReturnServerErrorWhenPhotoServiceCallFailed() {
    Long albumId = 2L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(500);
  }

  @Test
  void shouldReturnEmptyPhotos() {
    Long albumId = 3L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(200)
      .body("albumId", is(albumId.intValue()))
      .body("photos", hasSize(0));
  }
}

The tests don't need inline stub definitions because WireMock loads the mappings automatically from the classpath.

Test using the Testcontainers WireMock module

The Testcontainers WireMock module provisions WireMock as a standalone Docker container, based on WireMock Docker. This approach is useful when you want complete isolation between the test JVM and the mock server.

Create a mock configuration file at src/test/resources/com/testcontainers/demo/AlbumControllerTestcontainersTests/mocks-config.json:

{
  "mappings": [
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/([0-9]+)/photos"
      },
      "response": {
        "status": 200,
        "headers": {
          "Content-Type": "application/json"
        },
        "bodyFileName": "album-photos-response.json"
      }
    },
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/2/photos"
      },
      "response": {
        "status": 500,
        "headers": {
          "Content-Type": "application/json"
        }
      }
    },
    {
      "request": {
        "method": "GET",
        "urlPattern": "/albums/3/photos"
      },
      "response": {
        "status": 200,
        "headers": {
          "Content-Type": "application/json"
        },
        "jsonBody": []
      }
    }
  ]
}

Create the response body file at src/test/resources/com/testcontainers/demo/AlbumControllerTestcontainersTests/album-photos-response.json:

[
  {
    "id": 1,
    "title": "accusamus beatae ad facilis cum similique qui sunt",
    "url": "https://via.placeholder.com/600/92c952",
    "thumbnailUrl": "https://via.placeholder.com/150/92c952"
  },
  {
    "id": 2,
    "title": "reprehenderit est deserunt velit ipsam",
    "url": "https://via.placeholder.com/600/771796",
    "thumbnailUrl": "https://via.placeholder.com/150/771796"
  }
]

Create AlbumControllerTestcontainersTests.java:

package com.testcontainers.demo;

import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.Matchers.hasSize;
import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;

import io.restassured.RestAssured;
import io.restassured.http.ContentType;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;
import org.testcontainers.junit.jupiter.Container;
import org.testcontainers.junit.jupiter.Testcontainers;
import org.wiremock.integrations.testcontainers.WireMockContainer;

@SpringBootTest(webEnvironment = RANDOM_PORT)
@Testcontainers
class AlbumControllerTestcontainersTests {

  @LocalServerPort
  private Integer port;

  @Container
  static WireMockContainer wiremockServer = new WireMockContainer(
    "wiremock/wiremock:3.6.0"
  )
    .withMapping(
      "photos-by-album",
      AlbumControllerTestcontainersTests.class,
      "mocks-config.json"
    )
    .withFileFromResource(
      "album-photos-response.json",
      AlbumControllerTestcontainersTests.class,
      "album-photos-response.json"
    );

  @DynamicPropertySource
  static void configureProperties(DynamicPropertyRegistry registry) {
    registry.add("photos.api.base-url", wiremockServer::getBaseUrl);
  }

  @BeforeEach
  void setUp() {
    RestAssured.port = port;
  }

  @Test
  void shouldGetAlbumById() {
    Long albumId = 1L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(200)
      .body("albumId", is(albumId.intValue()))
      .body("photos", hasSize(2));
  }

  @Test
  void shouldReturnServerErrorWhenPhotoServiceCallFailed() {
    Long albumId = 2L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(500);
  }

  @Test
  void shouldReturnEmptyPhotos() {
    Long albumId = 3L;

    given()
      .contentType(ContentType.JSON)
      .when()
      .get("/api/albums/{albumId}", albumId)
      .then()
      .statusCode(200)
      .body("albumId", is(albumId.intValue()))
      .body("photos", hasSize(0));
  }
}

Here's what the test does:

The @Testcontainers and @Container annotations start a WireMockContainer using the wiremock/wiremock:3.6.0 Docker image.
withMapping() loads stub mappings from mocks-config.json, and withFileFromResource() loads the response body file.
@DynamicPropertySource overrides photos.api.base-url to point at the WireMock container's base URL.
The tests don't contain inline stub definitions because WireMock loads them from the JSON configuration files.

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Write tests with WireMock and Testcontainers

Test using WireMock JUnit 5 extension

Stub using JSON mapping files

Test using the Testcontainers WireMock module