Partial solution is to simulate executing the ODataQuery on a mock HttpClient.
First, the original method needs to be taken apart into two independent parts, one for building the query, the other for executing it. This is good design anyway, so no big problem:
private ODataQuery buildQuery(String path, String entity,
String sapClient, String sapLanguage) {
return ODataQueryBuilder
.withEntity(path, entity)
.withHeader("sap-client", sapClient, true)
.withHeader("sap-language", sapLanguage, true)
.withoutMetadata()
.build();
}
private ODataResponse executeQuery(ODataQuery query) {
return query.execute();
}
The buildQuery method can now be tested as follows:
@Test
public void addsSapLanguageToHeader() throws ODataException, IOException {
ODataQuery query = cut.buildQuery("api/v2", "business-partners", "", "fr");
HttpUriRequest request = getRequest(query);
assertContainsHeader(request, "sap-language", "fr");
}
The method getRequest produces a fake HttpClient that stubs all methods required to get query.execute(httpClient) to work. It stores the actual request and returns it for further inspection. Sample implementation with Mockito:
private HttpUriRequest getRequest(ODataQuery query) throws ODataException, IOException {
// stub methods to make code work
HttpResponse response = mock(HttpResponse.class);
when(httpClient.execute(any())).thenReturn(response);
StatusLine statusLine = mock(StatusLine.class);
when(response.getStatusLine()).thenReturn(statusLine);
HttpEntity entity = mock(HttpEntity.class);
when(response.getEntity()).thenReturn(entity);
InputStream inputStream = new ByteArrayInputStream("".getBytes(StandardCharsets.UTF_8));
when(entity.getContent()).thenReturn(inputStream);
Header[] headers = new Header[0];
when(response.getAllHeaders()).thenReturn(headers);
// simulate the execution of the query
query.execute(httpClient);
// grab the original argument from the mock for inspection
ArgumentCaptor<HttpUriRequest> captor = ArgumentCaptor.forClass(HttpUriRequest.class);
verify(httpClient).execute(captor.capture());
HttpUriRequest request = captor.getValue();
return request;
}
This solution is far from perfect, of course.
First, the amount of code needed to make this work alone shows how fragile this test will be over time. Whenever the CloudSDK decides to add a method or validation to the call sequence, this test will break. Note also that the test is invasive, by testing a private method, while gold standards say we should test only public methods.
Second, the method executeQuery can still not be tested. Execution paths also differ, because the test code uses the .execute(httpClient) variant to run the query, while the original code uses the .execute(destinationName) variant. The two happen to share code, but this may change over time.
