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Testing Webhook Receivers

Testing webhook receivers is similar to testing an API endpoint. The difference is that you have to follow the webhook provider's schema instead of defining it yourself.

Like with any API endpoint, you need to add testing in order to have high assurance in the correctness of the code. Though unlike API endpoints, good webhook providers support automatic retries with exponential backoff which means that the webhook provider will automatically recover from ephemeral errors.

In addition to correctness tests you should also test the servers to see how much load they can withstand and how to improve webhook processing. This will allow you to make the right decisions in order to scale your infrastructure to meet webhook processing demands.

Here we compare different processes you can use to identify and fix bugs in your webhook processing. You'll learn how to help scale your service appropriately and improve its performance.

Unit testing

Unit tests are used to test the smallest bits of your code, such as functions and classes. They usually involve defining an input and checking that the desired output is provided by your code.

For example, if your webhook endpoint handler does webhook verification, you should have tests to ensure that you verify things correctly.

Here are some other things you should have tests for:

  • Is the expected result achieved when input is supplied to this function?

  • Are calculations within functions/class methods correct?

  • How does your function handle bad input data?

  • Do your functions maintain data integrity?

Why you need unit tests for webhooks:

  • Find errors and remove them before they impact your users.

  • Can help surface bad error handling.

  • It is a lot less time-consuming to use code that has been thoroughly debugged and checked for errors.

Functional testing

Functional testing checks the behavior of a program by executing different sets of input values and evaluating the response. In other words, it makes sure every part is working together as intended.

A webhook URL is a specific endpoint on your app's API. It can be tested by simulating requests and checking the response.

There are many tools that help you test a webhook endpoint, though you can also just use good ol' cURL, or your favorite HTTP library.

Why you should have functional testing for webhooks:

  • Test webhook processing

  • Check for idempotency

  • Ensure data integrity

  • Observe error scenarios

  • Test authentication

Load testing webhooks

Load testing puts your app under pressure to see how many requests it can handle in a given time span before it starts missing requests.

Load tests are critical if you plan on processing a lot of webhooks. This will help you decide how to scale your app when traffic increases.

The Svix webhooks service supports per-endpoint rate-limiting. If you're receiving webhooks from a service that uses Svix, you can set a rate-limit to define the maximum load you're comfortable handling. Otherwise, you need to take extra care to ensure that your service stays up when a high load of webhooks are sent to your service.

Some metrics you should be tracking with load testing:

  • Requests per second

  • Total Requests

  • Failed Requests

  • Time per Request

Why you need load testing for webhooks:

  • To determine how much load your server can handle.

  • Inform any rate-limit setting you need to implement to prevent your server from crashing.

  • You'll know when to add additional servers to handle an increase in traffic.

Profiling performance

Profiling tests out a portion of your code to find any potential performance issues.

If you notice a dip in your code performance, it could be caused by slow operations per second or high request metrics. Having insight into performance bottlenecks can help you identify the precise issue and how to rewrite your webhook.

In order to profile your performance, you need a profiling tool. Profiling tools measure resource consumption of specific segments of code at runtime.

Using profiling reports, you can see how your resources are being allocated and which functions are consuming the most resources. This will help you determine the most important areas of optimization and get a higher level of performance.

Why you need to profile your app's performance:

  • Find out where the performance bottlenecks are

  • Find opportunities to increase performance


Testing is an important engineering practice that helps building high quality and stable codebases. Understanding the benefits of testing is the first step towards incorporating it into your development workflow. In this article, we looked at how to test your webhook endpoints to ensure they are reliable and dependable.

Testing webhooks leads to more robust webhooks handling, which means fewer bugs, less maintenance headaches, and smooth services.