Testing React Components with GraphQL APIs
When building React applications that interact with GraphQL APIs, testing can be a challenge. In this article, we’ll explore how to test React components that depend on GraphQL APIs, using the useQuery
hook from React Apollo and the MockedProvider
utility from @apollo/react-testing
.
Understanding GraphQL and React Apollo
Before diving into testing, let’s quickly review GraphQL and React Apollo. GraphQL is a query language for APIs that allows clients to specify exactly what data they need. React Apollo is a library that provides tools for interacting with GraphQL APIs in React applications.
The useQuery
Hook
One of the main functions provided by React Apollo is the useQuery
hook. This hook takes a GraphQL document as its first argument and returns a result object that includes the data, loading, and error statuses of the query request.
Mocking GraphQL Requests
To test React components that depend on GraphQL APIs, we need to mock the GraphQL requests. This is where MockedProvider
comes in. MockedProvider
is a utility from @apollo/react-testing
that allows us to create a mock version of the ApolloProvider component for testing purposes.
Testing Loading State
To test the loading state, we can wrap our components with MockedProvider
and provide an empty array as the value of the mocks prop. We can then assert that the component renders the expected text in its markup.
Testing Error State
To test the error state, we can wrap our components with MockedProvider
and provide mock request and error property values. We can then assert that the component correctly displays the expected error message.
Testing Success State
To test the success state, we can use MockedProvider
to wrap our components and provide mock values for the request and result properties. We can then assert that the component correctly displays the expected data.
Using waitFor
Utility
GraphQL API requests are asynchronous, so we often need to specify a waiting period in our tests before making assertions about the request’s outcome. The waitFor
utility from React Testing Library provides a way to handle this scenario.
Best Practices for Testing React Components with GraphQL APIs
- Use
MockedProvider
to mock GraphQL requests - Test loading, error, and success states
- Use
waitFor
utility to handle asynchronous requests - Keep tests independent and focused on specific scenarios
By following these best practices and using the tools provided by React Apollo and @apollo/react-testing
, we can write effective tests for our React components that interact with GraphQL APIs.