How to Test GraphQL API’s

How to Test GraphQL API’s

How to Test GraphQL API’s

Graph QL is simply a query language for APIs that collates specific data requested by a command with a single run, this is in contrast to RESTful architectural approach to software engineering.

Right now, owing to the amount of readily available tutorial resources, learning GraphQL is relatively easier than knowing how to run tests on it. This is mainly because the tools that you will likely come across support only RESTful.

As we go on in this article we are going to look at how to test GraphQL APIs and answer some frequently asked questions as you read along.

What is a Query in GraphQL?

What is a Query in GraphQL

Simply put, a Query in a GraphQL operation is how you fetch and read data requests from a server database. These values are then reflected or written to the end-user through a Mutation process.

It’s pretty much like a request in RESTFUL to GET an item from a server database. One outstanding feature of GraphQL is that it gives just enough control room to the client by allowing custom made queries by the client, specifically tailored to what they want to receive.

In essence what this means essentially is that both operations are requests that will prompt a GraphQL server to respond with specific data from a set.Doing all of this in as little as split seconds, the schema, queries, mutations, etc need to be tested to make sure the results are exactly as requested.

How do we test a Query in GraphQL?

A functionality test is undergone to make sure the Query is read and interpreted as should on the front-end.Considering factors like Machine Language, Test parameters and also the platform, one can choose from a list of test types to set up.

On average, EasyGraphQL is arguably the most popular tool out there for GraphQL functionality testing.

There are various test methods that can be used in any immediate case including;

  • Query tests: These are performed to ensure that the client-side request is responded to with the appropriate data collection.
  • Mutation tests: This is to make sure that a query is saved correctly on the database along with any modifications attached.
  • Load tests: This test process ensures the durability of the API (within SLAs) and how it performs under pressure, while taking in a high number of requests.
  • Security tests: Just as it’s called, the security tests check that the security details of each response is matched with the query and no sensitive data is allowed to pass without due process.

What is a mutation in GraphQL?

GraphQL is usually highlighted with its data retrieval, erroneously skipping the modification process -known as mutation- and how it’s written. 

A mutation query is there to read and translate the data sent for and bring out an understandable value. It can also be used as a channel to input, update or remove data which defines them as a part and parcel of the schema. 

Just as it is on RESTFUL, requests may have effects on the server side and cause for a data write. In any case, it helps to establish a prompt instance for every operation that prompts the parameters to be sent exclusively through a mutation process.

How do we test a mutation?

How do we test a mutation?

Mutation testing is what its name reads; testing based on mutations and modifications. The developer introduces minor modifications to the source code and in effect checks out if the test cases are able to pick up the small errors.

Ideally, codes in great condition won’t trigger any flags from the test case. If it does however this means that there is a defect in the code structure and -as it is put- the mutant lived. If the test code doesn’t detect any error then the mutant is dead. The goal is to kill all mutants.

The objective of mutation testing serves both ways in that the developer also knows when a test suite is effective and can have more tests that can kill more mutants. Reading further into the topic you’ll discover types of mutants like Survived Mutants, Equivalent mutants, etc.

Examples of mutation testing

For mutation testing, there are basically three types;

  • Value Mutations 
  • Decision Mutations 
  • Statement Mutations 

Value Mutation is the type of testing where the values are changed to detect errors in the program structure. Changes are primarily done on constants. Either a minute Value could be given to a much larger one, or vice versa.

In Decision Mutations, logical or calculated operations are changed to detect defects in the program structure.

Statement Mutation is the type conducted where a statement is deleted or is replaced by some other statement. 

An advantage of Mutation testing is that it brings attention to the errors in the program before it is released to be built upon.But on the flip side, it is time consuming as well as cost intensive.

What are input types in GraphQL schema?

In GraphQL an input type is what we call objects that are passed in parameters of a query, or any field. Object fields other than basic scalar types, list types, and other input types cannot be passed as input type. 

Input types are declared through two ways:  

  • Factory
  • @input Annotation

Factory as a method accepts All parameters including input type which are returned as an object when passed. Rules of how data is generated are set by a defined factory. Data saved through GraphQL queries on servers are deleted at the test latter end.

  • parameters of the factory are the same with the input type field.
  • @factory annotation must be instantiated by factory(ies)


  • @Factory annotation instantiated by a factory turns input types into objects.
  • While specifying the input type name, all factories should be kept in the same input type directory.
  • A given Factory classe should be enclosed in a container. The id factory should have the same class name as the factory container.
  • including @input annotation suffix to a named class changes it to input type. A class name can have several @input annotation suffixes which generate various links and names to different fields.

How to test Input types in GraphQL schema.

Testing each type ascertains if graphQL is valid or not. Runtime checks can be boycotted and will effectively inform developers once a void query has been created and reported by servers and clients.

  • Query a field in order to affirm if it exists on the type.
  • Specify what data that’s retrievable from the field.
  • Use inline fragments. It indicates what type that’s been queried.


  • A fragment will return a limitless result once it creates a cycle or refers to itself.
  • A field must return a scalar input type or an enum when executed.
  • Fields that exist on a character can only be executed.

What approach should one utilize?

Schema-approach involves stating set rules by SLD (Schema definition language). All Data structure stored in a graphql schema ensures the code follows its definition strictly. It’s basically the central truth for resolvers and clients.

Using code first approach

All programming languages have libraries that outline graphQL schema without having to write schema language. Programming languages creates the graphql schema and documentations.

Numerous resources, articles, tutorials and also communities aid the learning of either schema first approach or code first approach online. Try each approach as over time you would get to stick with a particular approach.

FAQs with answers

Can GraphQl API’s be tested with Postman?

Testing GraphQL API using Postman is relatively easy with the help of autocomplete support. Generating Queries and importing schema is absolutely allowed when testing GraphQL.

Should we hire a testing team?

Hiring a testing team would depend on how complex the GraphQL API data structure is.

Can GraphQL API testing be automated?

There are various automation tools used to test GraphQL APIs. Postman, Rest sharp, karate, TestProject are some tools that can be used.

How to automate GraphQL API testing?

Depending on the testing tool used. Automating graphQL can be generally done using a command line.

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