Testing Apollos reactive variables in Vuejs and GraphQL

We love Vue.js, we love GraphQL, we love testing, and we love Vue Apollo.

We have been having some great discussions in the office about how to test specific parts of Vue Apollo. They have a great guide on testing that allows you to assert that Mutations were sent, or you can test how a smart query's data causes the Component to render. These are great if your queries are static but what if you have dynamic or reactive variables on your query.

On one hand, you can test the dynamic nature of the query with an e2e test but that feels heavy-handed instead you can test the variables on your query directly.

Say you have this component

const wrapper = mountVue(GroupShow, {
  mocks: {
    $route: {
      params: { userId: this.$route.params.userId },
    },
  },
});

Then a simple test to say the queries variables could be

it('queries the correct group', () => {
  const data = {
    userId: 6,
  };

  const wrapper = mountVue(GroupsIndex, {
    mocks: {
      $route: {
        params: { userId },
      },
    },
  });

  wrapper.setData(data);

  expect(
    wrapper
      .vm
      .$options
      .apollo
      .groups
      .variables
      .bind(wrapper.vm)().userId,
  ).toEqual(6);
});

A couple of things to note.

1. I only feel obligated to test the variables function because I trust Vue Apollo to handle the variables correctly.
2. Notice the Function.bind call. When executing the function outside of Vue's event loop you don't have the same this so you need to bind back to the wrapper's view model.

Hopefully, this saves someone some time!