MockRestServiceServerAutoConfiguration with RestTemplate and RestClient together throws incorrect exception

[michaldo]

It should be possible to have together RestTemplate and RestClient in application and test them independently.

Unfortunately, currently if RestTemplate is used, RestClient cannot be tested:

org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerAutoConfiguration.DeferredRequestExpectationManager#getDelegate

if (!restTemplateExpectationManagers.isEmpty()) {
    Assert.state(restTemplateExpectationManagers.size() == 1,
            "Unable to use auto-configured MockRestServiceServer since "
                    + "MockServerRestTemplateCustomizer has been bound to more than one RestTemplate");
    return restTemplateExpectationManagers.values().iterator().next();
}
Assert.state(restClientExpectationManagers.size() == 1,
        "Unable to use auto-configured MockRestServiceServer since "
                + "MockServerRestClientCustomizer has been bound to more than one RestClient");
return restClientExpectationManagers.values().iterator().next();

[philwebb]

I'm not sure I understand your setup. Could you please provide a minimal sample project (either a GitHub project or zip file) that shows what you are trying to do.

[michaldo]

Voila: https://github.com/michaldo/rest-client-and-template-together

[mhalbritter]

The problem is in org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerAutoConfiguration.DeferredRequestExpectationManager#getDelegate:

When a RestTemplate is in the context, restTemplateExpectationManagers contains 1 entry, which is then always used. The expectation manager, which may be in restClientExpectationManagers is then ignored.

I suspect that the RestClient case then uses the wrong expectation manager when the mocked response is returned.

That's the error I'm getting:

java.lang.AssertionError: No further requests expected: HTTP GET /
0 request(s) executed.


	at org.springframework.test.web.client.AbstractRequestExpectationManager.createUnexpectedRequestError(AbstractRequestExpectationManager.java:193)
	at org.springframework.test.web.client.SimpleRequestExpectationManager.matchRequest(SimpleRequestExpectationManager.java:59)
	at org.springframework.test.web.client.AbstractRequestExpectationManager.validateRequest(AbstractRequestExpectationManager.java:91)
	at org.springframework.test.web.client.MockRestServiceServer$MockClientHttpRequestFactory$1.executeInternal(MockRestServiceServer.java:324)
	at org.springframework.mock.http.client.MockClientHttpRequest.execute(MockClientHttpRequest.java:126)
	at org.springframework.web.client.DefaultRestClient$DefaultRequestBodyUriSpec.exchangeInternal(DefaultRestClient.java:453)
	at org.springframework.web.client.DefaultRestClient$DefaultRequestBodyUriSpec.retrieve(DefaultRestClient.java:424)
	at com.example.restclientjson.RestClientAndTemplateTogetherTest.test(RestClientAndTemplateTogetherTest.java:42)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

[scottfrederick]

If you have two RestTemplate beans or two RestClient beans in your application, you can't use an auto-wired MockRestServiceServer in your test. If you do, you will get an exception with a message like Unable to use auto-configured MockRestServiceServer since MockServerRestTemplateCustomizer has been bound to more than one RestTemplate when you try to set an expectation. This is mentioned in the JavaDoc for AutoConfigureMockRestServiceServer.java but the language is not completely clear:

If multiple RestTemplates or RestClients are in use, inject a MockServerRestTemplateCustomizer and use getServer(RestTemplate), or inject a MockServerRestClientCustomizer and use getServer(RestClient.Builder), or bind a MockRestServiceServer directly.

The same is true when you have one RestTemplate and one RestClient, but this condition is not currently detected in the code like it should be so that an exception with a descriptive message can be thrown. We'll fix that.

Applying the suggestion from the JavaDoc to the provided sample would look like this:

    @Test
    void test(@Autowired RestClient restClient, @Autowired MockServerRestClientCustomizer customizer) {

        // given
        customizer.getServer().expect(requestTo("/")).andRespond(withSuccess());

        // when then
        restClient.get()
                .uri("/")
                .retrieve();
    }