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Postman API Testing Tips

Can You Use Postman With Graphql

API Testing Blog

Working with GraphQL in Postman

While Postman is primarily known for its REST API testing capabilities, it can also be effectively used for testing GraphQL APIs. Although Postman doesn’t natively support GraphQL, with some configuration and custom tooling, we can achieve seamless GraphQL testing within the platform.

Understanding GraphQL in Postman

GraphQL is a query language for APIs, offering a more flexible and efficient way to interact with data compared to traditional REST APIs. Instead of predefined endpoints, GraphQL utilizes a schema that defines the available data and lets you specify precisely what data you need.

Utilizing Postman’s GraphQL Support

While Postman doesn’t offer built-in GraphQL support like dedicated GraphQL clients, it allows us to leverage its powerful features by using custom code and extensions.

1. Using the Postman GraphQL Collection:

A popular approach is using a dedicated Postman collection designed for GraphQL requests. These collections usually have predefined request templates for common GraphQL operations like queries, mutations, and subscriptions.

2. Defining GraphQL Queries and Mutations:

  • Write Raw GraphQL Queries: Inside your Postman request, create a new body tab and choose “raw”. Define the GraphQL query or mutation in your chosen language (e.g., JSON, GraphQL).

    query {
      user(id: 1) {
        name
        email
      }
    }

  • Using the GraphQL Variables Tab: Postman allows you to define variables for your queries and mutations. This promotes reusability and data separation. Create a new “Variables” tab, and define your variables:

    {
      "userId": 1
    }

    Then, reference these variables in your GraphQL query:

    query {
      user(id: $userId) {
        name
        email
      }
    }

3. Setting Up Headers:

For GraphQL APIs, the Content-Type header usually needs to be set to application/json.

4. Sending GraphQL Requests

Clicking the “Send” button in Postman will execute your GraphQL request. Postman handles the request and displays the response in the body, much like it does with REST API requests.

Practical Example with Step-by-Step Guide

Let’s use a simple GraphQL API (like the “Star Wars” API) to demonstrate testing a GraphQL query in Postman.

1. Open Postman: Create a new request.

2. Set up the request details:

  • Method: POST
  • URL: https://swapi.dev/graphql

3. Define your GraphQL query:

Create a new “body” tab, choose “raw,” and select “GraphQL” as the language:

query {
  character(id: 1) {
    name
    birthYear
    homeworld {
      name
    }
  }
}

4. Set the headers:

In the “Headers” tab, add the following:

Key: Content-Type
Value: application/json

5. Execute and View the Response:

Click “Send” to execute your request. Postman will return the JSON response in the body, containing the requested data.

6. Inspect the Response:

The response body will display the results of your GraphQL query in JSON format.

Additional Tips for GraphQL Testing in Postman

  • Utilize the “Test” tab: You can add assertions in Postman’s “Test” tab, validating the response data and ensuring your API is functioning correctly. You can even check for specific values or status codes.
  • Implement Pre-request Scripts: Postman’s pre-request scripts can be used to dynamically generate GraphQL queries or manage variables before sending requests.
  • Consider using GraphQL clients: Dedicated GraphQL clients like Insomnia or GraphiQL offer a more user-friendly experience and provide additional debugging and introspection tools. However, for basic and quick testing, Postman proves effective.

Benefits of Using Postman for GraphQL Testing

  • Familiar Environment: Postman provides a user-friendly and familiar environment for developers and testers, familiar with its RESTful API testing functionalities.
  • Collaboration and Sharing: Share your GraphQL requests, tests, and collections with your team, enabling collaboration and streamlined testing processes.
  • Powerful Features: Postman offers features like variables, test scripts, environments, and collections, which are beneficial for creating robust GraphQL tests.
  • Request and Response Visualization: Postman offers easy-to-understand visualizations of your GraphQL requests and responses.

Using Postman effectively allows for a more integrated approach to your API testing workflow, even when dealing with GraphQL APIs, extending the benefits of this valuable tool to a wider range of testing needs.

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