Brtdku

I have a Spring Boot test that uses wiremock to mock an external service. In order to avoid conflicts with parallel builds I don't want to set a fixed port number for wiremock and would like to rely on its dynamic port configuration.

The application uses a property (external.baseUrl) set in the application.yml (under src/test/resources). However I didn't find a way to programmatically override that. I've tried something like this:

    WireMockServer wireMockServer = new WireMockServer();

    wireMockServer.start();

    WireMock mockClient = new WireMock("localhost", wireMockServer.port());

    System.setProperty("external.baseUrl", "http://localhost:" + wireMockServer.port());

but it didn't work and the value in application.yml was used instead. All other solutions that I've looked at override the property with a static value (for example in some annotation), but I don't know the value of the wiremock port until the test is run.

Clarification:

Both spring boot and wiremock run on random ports. That's fine and I know how to get the value of both ports. However wiremock is supposed to mock an external service and I need to tell my application how to reach it. I do this with the external.baseUrl property. The value I want to set in my test depends of course on the wiremock port number. My problem is simply how to programmatically set a property in a spring boot test.

Consider using Spring Cloud Contract Wiremock

There is already JUnit Rule builder which allows to specify ${wiremock.port}
to set random port in property/yaml files

Or you can use WireMockRestServiceServer to bind wiremock to your RestTemplate so you don't even need to override url in your tests

I could not find a way to override properties in a Spring Boot integration test, since the test is run only after the application is created and all the beans already configured.

As a work around I added a @TestConfiguration to the test to replace the beans in the application:

private static WireMockServer wireMockServer1 = getWireMockServer();

private static WireMockServer wireMockServer2 = getWireMockServer();

private static WireMockServer wireMockServer3 = getWireMockServer();



private static WireMockServer getWireMockServer() {

    final WireMockServer wireMockServer = new WireMockServer(options().dynamicPort());

    wireMockServer.start();

    return wireMockServer;

}



@TestConfiguration

static class TestConfig {

    @Bean

    @Primary

    public BeanUsingAProperty1 getBean1() {

        BeanUsingAProperty myBean = new BeanUsingAProperty();

        myBean.setPort(wireMockServer.port());

        return myBean;

    }



    @Bean

    @Primary

    public BeanUsingAProperty2 getBean2() {

        String baseUrl = "http://localhost:" + wireMockServer2.port();

        return new BeanUsingAProperty2(baseUrl);

    }



    @Bean

    @Primary

    public BeanUsingAProperty3 getBean3() {

        String baseUrl = "http://localhost:" + wireMockServer3.port() + "/request";

        return new BeanUsingAProperty3(new RestTemplate(), baseUrl, "someOtherParameter");

    }

}

This effectively replaced the BeanUsingAProperty with the one defined in the test so that it has the correct port number for Wiremock.

For this configuration to be picked up I had to add this class in the test annotation

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT, classes = {

    MySpringBootApplication.class, MyIntegrationTest.TestConfig.class })

Note that I use the non-static Wiremock API, since I have several such external services that each need to be mocked. Note that how the different beans are built is different depending on how each was designed.

Use property substitution in your application.properties:

external.baseUrl=http://exampleUrl:${wiremock.server.port}

This requires the wiremock.server.port property to be set before the SpringBootTest is initialised, which can be achieved by adding the @AutoConfigureWireMock annotation to your test class.

What about this:

@SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)

class YourTestClass {

    @LocalServerPort

    int port;



    public void test() {

        WireMockServer wireMockServer = new WireMockServer(port);

        wireMockServer.start();

        WireMock mockClient = new WireMock("localhost", port);

    }

}

The approach I use to programmatically change a property when starting a Spring Boot app, is to pass the custom value into the application main entry-point String args. This will have the effect of over-riding all other means such as System properties, YML or other config files.

Here is an example:

String args = new String{"--my.prop=foo"};

SpringApplication.run(Application.class, args);

It will be easy for you to expose a static method or custom API which starts the Spring Boot app (for testing) and with the value you want.

And then, once you have the value of the wiremock port - things are easy. Here is an example: PaymentServiceContractTest.java

P.S. Karate (the open-source test examples I am using above) is a new alternative to WireMock, do check it out ;)

How are you reading external.baseUrl?
If you are using a @Value annotated property, you can use ReflectionTestUtils to set the port after you have setup the mock server.

ReflectionTestUtils.setField(yourTestClass, "youPort",  wireMockServer.port());