### Question:
UserApi { public User getUserByName(String username) throws ApiException { Object localVarPostBody = null; if (username == null) { throw new ApiException(400, "Missing the required parameter 'username' when calling getUserByName"); } String localVarPath = "/user/{username}".replaceAll("\\{format\\}","json") .replaceAll("\\{" + "username" + "\\}", apiClient.escapeString(username.toString())); List<Pair> localVarQueryParams = new ArrayList<Pair>(); Map<String, String> localVarHeaderParams = new HashMap<String, String>(); Map<String, String> localVarCookieParams = new HashMap<String, String>(); Map<String, Object> localVarFormParams = new HashMap<String, Object>(); final String[] localVarAccepts = { "application/xml", "application/json" }; final String localVarAccept = apiClient.selectHeaderAccept(localVarAccepts); final String[] localVarContentTypes = { }; final String localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes); String[] localVarAuthNames = new String[] { }; GenericType<User> localVarReturnType = new GenericType<User>() {}; return apiClient.invokeAPI(localVarPath, "GET", localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localVarReturnType); } UserApi();  UserApi(ApiClient apiClient); ApiClient getApiClient(); void setApiClient(ApiClient apiClient); void createUser(User body); void createUsersWithArrayInput(List<User> body); void createUsersWithListInput(List<User> body); void deleteUser(String username); User getUserByName(String username); String loginUser(String username, String password); void logoutUser(); void updateUser(String username, User body);  }### Answer:
@Test public void getUserByNameTest() throws ApiException { String username = null; User response = api.getUserByName(username); }