Unit testing Apollo useMutation onCompleted

Question

I have an onCompleted that I am trying to test from my useMutation, I am using jest and react-testing-library. This is the piece of code I am trying to test

this is my react code:

const [deleteJobs] = useMutation<DeleteJobsMutation, MutationDeleteJobsArgs>(
mutationQuery,
{
  refetchQueries: refetchQueries as string[],
  onCompleted: () => (callback ? callback() : onCancel?.(null)),
},)

my mutation:

mutation deleteJobs($jobIds: [ID!]!) { deleteJobs(jobIds: $jobIds) {
successful}}

I have managed to mock it so it does call and I have also mocked it to succeed so I can test scenarios on success but I can't seem to work out how to get it to trigger the onCompleted

Answer 1

Apollo Client's test suite has an example that demonstrates how to mock and test useMutation's onCompleted callback:

it('should allow passing an onCompleted handler to the execution function', async () => {
  const CREATE_TODO_DATA = {
    createTodo: {
      id: 1,
      priority: 'Low',
      description: 'Get milk!',
      __typename: 'Todo',
    },
  };

  const mocks = [
    {
      request: {
        query: CREATE_TODO_MUTATION,
        variables: {
          priority: 'Low',
          description: 'Get milk.',
        }
      },
      result: {
        data: CREATE_TODO_DATA,
      },
    }
  ];

  const { result } = renderHook(
    () => useMutation<
      { createTodo: Todo },
      { priority: string, description: string }
    >(CREATE_TODO_MUTATON),
    { wrapper: ({ children }) => (
      <MockedProvider mocks={mocks}>
        {children}
      </MockedProvider>
    )},
  );

  const createTodo = result.current[0];
  let fetchResult: any;
  const onCompleted = jest.fn();
  const onError = jest.fn();
  await act(async () => {
    fetchResult = await createTodo({
      variables: { priority: 'Low', description: 'Get milk.' },
      onCompleted,
      onError,
    });
  });

  expect(fetchResult).toEqual({ data: CREATE_TODO_DATA });
  expect(result.current[1].data).toEqual(CREATE_TODO_DATA);
  expect(onCompleted).toHaveBeenCalledTimes(1);
  expect(onCompleted).toHaveBeenCalledWith(CREATE_TODO_DATA);
  expect(onError).toHaveBeenCalledTimes(0);
});