Скачать или смотреть Resolving the Rspec Double Leak Issue in Your Tests

Learn how to effectively manage and mock external client requests in Rspec tests to prevent double leakage issues.
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This video is based on the question https://stackoverflow.com/q/65276431/ asked by the user 'Rafael Costa' ( https://stackoverflow.com/u/7219974/ ) and on the answer https://stackoverflow.com/a/65289076/ provided by the user 'Rafael Costa' ( https://stackoverflow.com/u/7219974/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Rspec Double Leakage in Tests

When working with Rspec, especially while testing classes that make external requests, you may encounter a frustrating issue: the infamous double leakage. This problem arises when a mock object (a double) is created in one test example but inadvertently interferes with another, leading to errors and failed tests.

In this guide, we will explore a specific case involving double leakage in Rspec and how to solve it effectively. This will enhance your testing skills and help maintain the integrity of your test suite.

The Problem: Double Leakage in Rspec

Let’s take a look at a sample scenario where double leakage occurred:

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

What Went Wrong?

In the above example, the first test (creates something) passes as expected, but the subsequent test (calls client) fails with the following error:

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

This indicates that the client_double was reused across multiple test examples, which violates Rspec’s principle that doubles should exist within the scope of a single example.

The Solution: Instantiate Instead of New

So how do we resolve this issue? It turns out that the underlying problem stemmed from using a singleton-like behavior in the client. The solution involved switching from mocking the new method to mocking the instantiate method of the Client::Base class:

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

Why This Works

By changing our mock from new to instantiate, we prevent the client_double from being cached or retained in state between tests. Instead, we ensure that a new instance of the client double is created each time a test runs.

Summary

In conclusion, managing external client requests in Rspec tests requires careful handling of doubles to avoid leakage across examples. The key takeaway is:

Use instantiate instead of new when mocking classes that might induce singleton behavior or maintain state between test examples.

By adopting this approach, you can ensure cleaner tests, enhanced predictability, and a more robust testing framework.

Happy testing!