Effective Testing of React Components with GraphQL APIs

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.