Mockito Unit Test with HTTPUrlConnection - spring-boot

Question

I wrote code in our Spring Boot 2 application to make a third-party API call with HTTPUrlConnection.
public String loginApi(LoginDTO loginDto)
{
String responseData = null;
HttpURLConnection conn = null;
try {
link = authBaseUrl + loginUrl;
url = new URL(link);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty(CONTENT_TYPE, MEDIA_TYPE);
String body = getAuth0LoginDto(loginDto);
// =====================
// For POST only - START
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
os.write(body.getBytes(StandardCharsets.UTF_8));
os.flush();
os.close();
// For POST only - END
// ====================
try (BufferedReader br = (conn.getResponseCode() >= 400
? new BufferedReader(new InputStreamReader(conn.getErrorStream()))
: new BufferedReader(new InputStreamReader(conn.getInputStream())))) {
StringBuilder everything = new StringBuilder();
String output = null;
while ((output = br.readLine()) != null) {
everything.append(output);
}
responseData = everything.toString();
}
} catch (JsonProcessingException e) {
throw new Auth0Exception("Could not create Auth0 Login Body", e);
} catch (IOException e) {
throw new Auth0Exception("Error with Login API", e);
} finally {
if (conn != null) {
conn.disconnect();
}
}
return responseData;
}
Now, I am very much used to doing real integration testing, where I make a real call to the web-service and check the results.
I am now being asked to use strictly Mockito, not PowerMockito, not EasyMock, to create mocking tests, and I have never done that before. My knowledge of Mockito is weak also since I haven't used it in a very long time.
So, I know it has been asked before, and I have really searched on the internet, and I really haven't found a full piece of code as an example. I see code snippets which leaves me with pieces missing, and I am not knowledgeable enough to add those parts myself.
I know this code actual implementation works fine, and the integration test works fine also. But, what I have seen before is that some users are being told they need to change their client code in order to make the mockito tests work.
If I don't get the mocking tests working for HTTPUrlConnection, then I'll be forced to switch over to RestTemplate and Mocking since my co-worker insists we use RestTemplate anyway.
Thanks!

Answer 1

Since you have asked for a small example which does not make sense but should show the idea:
import java.io.IOException;
import java.io.UncheckedIOException;
import java.net.HttpURLConnection;
import java.net.URL;
public class App {
public int status(URL url) {
HttpURLConnection urlConnection = null;
try {
urlConnection = create(url);
return urlConnection.getResponseCode();
} catch (IOException e) {
throw new UncheckedIOException(e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
}
HttpURLConnection create(URL url) throws IOException {
return (HttpURLConnection) url.openConnection();
}
}
I would implement this with a spy and as I recommended a mocked HttpURLConnection:
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.Spy;
import org.mockito.junit.jupiter.MockitoExtension;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.doReturn;
#ExtendWith(MockitoExtension.class)
class AppTest {
#Spy
App app;
#Mock
HttpURLConnection connection;
#Test
void status() throws IOException {
int expected = 200;
doReturn(connection).when(app).create(any());
doReturn(expected).when(connection).getResponseCode();
URL url = new URL("http://www.google.ats");
int status = app.status(url);
Assertions.assertEquals(expected, status);
}
}