When using MockRestServiceServer cannot precisely test number of service calls - rest

Question

I am coding some retry logic for a service call, and attempting to test that the Rest Template is attempting to hit the service a certain number of times, in a unit test. I am using the following code to perform the test.
MockRestServiceServer mockServer = MockRestServiceServer.bindTo(restTemplate).build();
mockServer.expect(ExpectedCount.times(5), method(HttpMethod.GET))
.andRespond(withServerError());
service.call();
I have the retry logic set to only make two attempts. The above test code requires that it occur five times, but the test always passes. In fact, the only way I can get this test to fail is by setting the expected count to one (anything less than the number of actual invocations). The same sort of problem occurs when I use ExpectedCount.min or ExpectedCount.between in that the test will only fail when actual invocations exceed expectation.
I need to be able to test for an exact number of service calls, preferably without the use of Mockito.

Answer 1

This is what finally worked for me, testing with a max attempts of 4:
MockRestServiceServer server;
#Before
public void setUp() {
server = MockRestServiceServer.bindTo(restTemplate).build();
}
#After
public void serverVerify() {
server.verify();
}
#Test
public void doWork_retryThenSuccess() throws Exception {
final String responseBody = "<some valid response JSON>";
final String url = BASE_URL + "/doWork";
server.expect(requestTo(url))
.andExpect(MockRestRequestMatchers.method(HttpMethod.POST))
.andRespond(ExceptionResponseCreator.withException(new SocketTimeoutException("first")));
server.expect(requestTo(url))
.andExpect(MockRestRequestMatchers.method(HttpMethod.POST))
.andRespond(ExceptionResponseCreator.withException(new IOException("second")));
server.expect(requestTo(url))
.andExpect(MockRestRequestMatchers.method(HttpMethod.POST))
.andRespond(ExceptionResponseCreator.withException(new RemoteAccessException("third")));
server.expect(requestTo(url))
.andExpect(MockRestRequestMatchers.method(HttpMethod.POST))
.andRespond(withSuccess(responseBody, MediaType.APPLICATION_JSON));
final MyResponseClass response = myService.call();
assertThat(response, notNullValue());
// other asserts here...
}
We are constrained to use Spring Test 5.0.10, which doesn't have MockRequestResponseCreators.withException() (method was added in 5.2.2). Borrowing from Spring 5.2.7 code, this works well:
package com.company.test;
import java.io.IOException;
import org.springframework.remoting.RemoteAccessException;
import org.springframework.test.web.client.ResponseCreator;
import org.springframework.test.web.client.response.MockRestResponseCreators;
public class ExceptionResponseCreator extends MockRestResponseCreators {
public static ResponseCreator withException(IOException ex) {
return request -> { throw ex; };
}
public static ResponseCreator withException(RemoteAccessException ex) {
return request -> { throw ex; };
}
}

Answer 2

You can create your own ResponseCreator with the logic you want. For example:
class DelegateResponseCreator implements ResponseCreator {
private final ResponseCreator[] delegates;
private int toExecute = 0;
public DelegateResponseCreator(final ResponseCreator... delegates) {
this.delegates = delegates;
}
#Override
public ClientHttpResponse createResponse(final ClientHttpRequest request) throws IOException {
ClientHttpResponse ret = this.delegates[this.toExecute % this.delegates.length].createResponse(request);
this.toExecute++;
return ret;
}
}
This delegator executes the ResponseDelegates in order.
So you can mock the response for the call number you want
mockServer.expect(ExpectedCount.times(5), MockRestRequestMatchers.method(HttpMethod.GET))
.andRespond(new DelegateResponseCreator(
MockRestResponseCreators.withServerError(),
MockRestResponseCreators.withServerError(),
MockRestResponseCreators.withServerError(),
MockRestResponseCreators.withServerError(),
MockRestResponseCreators.withSuccess()
));
In this example, the first four calls will return a server error whereas the fifth will be a success.

Answer 3

You need to call mockServer.verify() after making all your requests to check if the expectations are met. Otherwise, you can get away with never making any requests.