GraphQL Testing in 2024: Benefits, Types & Components

GraphQL is an open-source query and manipulation language for APIs developed by Facebook. Industry leaders and big companies such as Facebook, Airbnb, and Github are adopting GraphQL.¹ Developers use GraphQL in conjunction with REST APIs or sometimes even as a direct alternative.

Just like REST API testing, GraphQL testing is necessary for users to ensure the stability of GraphQL APIs. Contrary to REST API testing, however, GraphQL testing can be challenging because few tools support GraphQL. This article aims to close the information gap by giving information about the types and components of GraphQL testing.

What is GraphQL testing?

Figure 1: Representation of GraphQL 

The main objective of GraphQL testing is to ensure that the schemas, queries, and mutations created for an API operate as expected. As GraphQL is a service located between front-end systems and backend APIs, GraphQL testing is crucial for maintaining the stability of the services offered by APIs.

GraphQL has a single endpoint (see Figure 1 above), making it a direct connection between the data source and the customer. For that reason, GraphQL is essential for testing purposes.

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Top 3 benefits of GraphQL Testing 

GraphQL testing provides the following benefits:

1. Better overview of applications: GraphQL testing will enable the tester to understand better objects and data structures returned by the queries.
2. Eliminate unforeseen bugs: GraphQL is flexible, and testing helps users ensure that the number of errors is minimal.
3. Stability: GraphQL testing improves the overall quality and stability of GraphQL APIs by checking and ensuring the functions of queries, resolvers, schemas, and mutations.

Types of GraphQL testing 

There are multiple methods for testing GraphQL:

• Static type checking: It is beneficial to use a language with static type checking, such as JavaScript or its extensions. The number of errors between the schemas and resolvers will be smaller thanks to the static type-checking method’s

We can implement the Trophy Scheme to get an idea for the preference of the methods (See Figure 2).

 Figure 2: The Testing Trophy 

Source: Medium²

We list the reasoning behind the testing trophy (see Figure 2) as follows: 

• Static type checks the code and shows if there is anything wrong.
• Unit tests are relatively easy to make because they test small units of code and can run fast. 
• Integration tests are slower because they test multiple layers of code. The tester can use server mock and check the fluxes of the test.
• End-to-End tests are much slower and harder to make because they involve multiple products such as servers, clients, and databases. These tests are used to check a routine.

Components to test in GraphQL

Here are the following components you should conduct test on:

• Schema: Schemas can be tested using static type checks and mock schema & test queries.
• Query: An automated approach can be used to test queries using libraries such as “request” and “supertest”. GraphiQL³ is also an easy way to test queries if GraphQL servers are built using JavaScript. EasyGraphQL tester can be also implemented by the user to test different queries.
• Mutations: Mutations can be tested by using EasyGraphQL’s tester function or GraphiQL’s mutation query in its client. It will ensure that the database functions properly.
• Resolvers: EasyGraphQL’s tester library can be used to test resolvers, resolvers are Javascript functions so they can be tested just as another Javascript code. 

Which tools to test the components of GraphQL?

EasyGraphQL⁴ is one of the widely used tools for GraphQL testing. You can run it on every JavaScript implementation of GraphQL. You can also mock the results of queries and test against them.

Testing schema

We can use static type checks, mock schema and test queries for schema testing. The libraries, graphql-schema-linter⁵ and eslint-plugin-graphql⁶can be used to perform schema testing.

Est-lint-plugin-graphql is a linter to extend Eslint rules, and graphql-schema-linter is a tool to validate the schema definition. In addition to static type checks, mocking the schema using a mock-server via graphql-tools⁷(a set of npm packages) while paying attention to possible combinations will be beneficial for schema testing.

Testing queries and mutations

While we can use an automated approach by using libraries “request” and “supertest” for query testing, we can mock queries and mutations via easygraphql-tester.⁸ We can also make test assertions directly via easygraphql-tester instead of mocking. Below, you can see the direct test assertion example.

Source: NDC Conferences⁹

Testing Resolvers

Resolvers are pure functions, and they are easier to test. We don’t need packages to test resolvers; they are just javascript functions or whichever language the GraphQL server is based on. Resolvers collect information from schemas, thus it is necessary to test them early on to avoid costly errors. Here is an example for resolve testing:

Source: NDC Conferences ¹⁰

If you have further questions concerning API testing you can reach us:

External Links

• 1. S. L. Vadlamani, B. Emdon, J. Arts and O. Baysal, “Can GraphQL Replace REST? A Study of Their Efficiency and Viability,” 2021 IEEE/ACM 8th International Workshop on Software Engineering Research and Industrial Practice (SER&IP), 2021, pp. 10-17.https://ieeexplore.ieee.org/abstract/document/9474834.
• 2. Medium https://medium.com/@poloo.p3/what-is-frontend-testing-and-how-do-i-have-tested-it-540e12335317
• 3. https://github.com/graphql/graphiql
• 4. https://github.com/EasyGraphQL/easygraphql-tester
• 5. GrahpQL Schema Linter https://github.com/cjoudrey/graphql-schema-linter
• 6. Apollo GraphQL https://github.com/apollographql/eslint-plugin-graphql
• 7. GraphQL Tools. https://www.the-guild.dev/graphql/tools
• 8. https://github.com/EasyGraphQL/easygraphql-tester
• 9. NDC Conferences. Testing GraphQL: From Zero To Hundred Percent – Roy Derk https://www.youtube.com/watch?v=qVyPAU1Y9nk
• 10. NDC Conferences. Testing GraphQL: From Zero To Hundred Percent – Roy Derk https://www.youtube.com/watch?v=qVyPAU1Y9nk