Resolver unit tests in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a basic resolver function that returns a fixed string.

GraphQL

const resolvers = { Query: { hello: () => [1] } };

Drag options to blanks, or click blank then click option'

A"Hello, world!"

BHello, world!

Creturn "Hello, world!"

Dconsole.log("Hello, world!")

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Using console.log instead of returning a value

The resolver must return a string value. Using quotes returns the string correctly.

2fill in blank

medium

Complete the resolver to accept arguments and return the name argument.

GraphQL

const resolvers = { Query: { greet: (_, [1]) => name } };

Drag options to blanks, or click blank then click option'

Acontext

Bargs

C{ name }

Dinfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong parameter name

Not destructuring the argument object

The resolver receives arguments as the second parameter. Destructuring { name } extracts the name argument.

3fill in blank

hard

Fix the error in the resolver that tries to return a user by id from a data source.

GraphQL

const resolvers = { Query: { user: (_, { id }, [1]) => [1].dataSources.userAPI.getUserById(id) } };

Drag options to blanks, or click blank then click option'

Ainfo

Bcontext

Cargs

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter name for context

Trying to access dataSources from args

The third parameter is the context, which contains dataSources. Using 'context' allows access to userAPI.

4fill in blank

hard

Fill both blanks to write a test that mocks the data source and checks the resolver output.

GraphQL

test('user resolver returns user data', async () => {
  const mockUser = { id: '1', name: 'Alice' };
  const context = { dataSources: { userAPI: { getUserById: jest.fn().mockResolvedValue([1]) } } } };
  const result = await resolvers.Query.user(null, { id: '1' }, [2]);
  expect(result).toEqual(mockUser);
});

Drag options to blanks, or click blank then click option'

AmockUser

Bcontext

CmockUser.id

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Not passing context to the resolver

Mocking the wrong return value

The mockResolvedValue should return the mockUser object. The context parameter must be passed to the resolver.

5fill in blank

hard

Fill all three blanks to write a test that verifies the resolver throws an error when user is not found.

GraphQL

test('user resolver throws error if user not found', async () => {
  const context = { dataSources: { userAPI: { getUserById: jest.fn().mockResolvedValue([1]) } } } };
  await expect(resolvers.Query.user(null, { id: '2' }, [2])).rejects.toThrow([3]);
});

Drag options to blanks, or click blank then click option'

Anull

Bcontext

C"User not found"

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Not mocking null return value

Not passing context to resolver

Expecting wrong error message

The mock returns null to simulate no user found. The context is passed to the resolver. The test expects an error with message 'User not found'.