Scala Integration Tests for Caliban GraphQL Subscriptions

Discover how to effectively implement integration tests for GraphQL subscriptions in Caliban using Play Framework with detailed step-by-step instructions.
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Introduction to Testing GraphQL Subscriptions

If you're working with a Caliban GraphQL application integrated with the Play Framework, you might have aced your integration tests for queries and mutations. However, when it comes to testing subscriptions over websockets, you might find yourself in uncharted territory. While there's ample information available for conventional testing methods, guidance on websocket testing—especially for GraphQL subscriptions—remains scarce.

In this post, we'll address how to properly set up your integration tests for subscriptions and ensure your testing process is both efficient and effective.

Understanding GraphQL Subscriptions

Before we dive into the implementation, let's clarify what GraphQL subscriptions are. They allow clients to listen to real-time updates from the server. For instance, when data changes (like a new chat message or an updated stock price), the server sends a notification to all connected clients that have subscribed to a certain topic.

The Challenge with Websockets in Play Framework

Typically, testing for queries and mutations involves standard fake requests routed through a Play application. In contrast, subscriptions necessitate establishing a websocket connection, which complicates the testing process.

A Step-by-Step Guide to Testing GraphQL Subscriptions

To successfully conduct integration tests for GraphQL subscriptions, follow these steps:

Step 1: Set Up Your Websocket Protocol

Begin by setting the websocket header correctly on the client side:

[[See Video to Reveal this Text or Code Snippet]]

This header ensures that the connection adheres to the GraphQL websocket protocol for handling subscriptions.

Step 2: Initialize the Websocket Connection

Once the header is set up, send the initial connection request to the server with the following payload:

[[See Video to Reveal this Text or Code Snippet]]

This request signals to the server that a new websocket connection is being established.

Step 3: Acknowledge the Connection

After the server acknowledges the connection with a connection_ack message, you're ready to start your subscription:

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Here, you will replace subscriptionQuery with your actual GraphQL subscription query.

Step 4: Implement a Sample Code

Here’s a concise example demonstrating how to implement the steps discussed above:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Testing GraphQL subscriptions in a Caliban application using the Play Framework might seem intimidating due to the reduced resources and complexity of websockets. However, by following the outlined steps—properly setting up the websocket headers, initiating connections, acknowledging them, and sending subscription queries—you can conduct effective integration tests.

Feel free to experiment with the provided code snippets and tweak them to fit your specific application needs. Happy testing!