Added test to make sure that the response id field is not null. (#55)

src/test/java/com/bunq/sdk/http/ErrorResponseTest.java

@@ -0,0 +1,32 @@
+package com.bunq.sdk.http;
+
+import com.bunq.sdk.BunqSdkTestBase;
+import com.bunq.sdk.exception.ApiException;
+import com.bunq.sdk.model.generated.endpoint.UserPerson;
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+
+public class ErrorResponseTest extends BunqSdkTestBase {
+  /**
+   * Invalid user id to trigger BadRequestException
+   */
+  private static final int INVALID_USER_PERSON_ID = 0;
+
+  /**
+   */
+  @Test
+  public void badRequestWitResponseIdTest()
+  {
+    ApiException caughtException = null;
+
+    try {
+      UserPerson.get(getApiContext(), INVALID_USER_PERSON_ID);
+    } catch (ApiException $exception) {
+      caughtException = $exception;
+    }
+
+    assertNotNull(caughtException);
+    assertNotNull(caughtException.getResponseId());
+  }
+}