How to Pass a Test Fixture to a Helper Function in C+ + GTest

Learn how to effectively call protected static methods from a helper function in C+ + GTest by leveraging inheritance and proper scoping.
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How to Pass a Test Fixture to a Helper Function in C+ + GTest: A Step-by-Step Guide

C+ + GTest offers a robust framework for unit testing, including the use of test fixtures that encapsulate shared state and behavior for multiple tests. However, when you have a protected static method within a test fixture that you want to call from a helper function, you might encounter accessibility issues. This post details how to address this challenge effectively.

The Problem Statement

You have a test fixture defined in your test class, and it contains a protected static method you wish to call from a separate helper function. The crux of the problem lies in the fact that protected methods can only be accessed via derived classes or within the same class. Your specific requirements make it impossible to simply call the method from within the test function.

Example Scenario

Here’s an example to illustrate the issue:

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In the above scenario, trying to call fixture_func from helper_func results in an accessibility error because fixture_func is a protected method.

The Solution

To solve this problem, you need to make fixture_func accessible to the helper_func. Fortunately, there are various techniques you can take, summarized below:

1. Use Inheritance to Extend Visibility

One method to call a protected method from within a non-member function is to create a derived class from the test fixture that makes the method public. Here’s how you can do it:

Creating a Derived Class

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Updating the Helper Function

Now you can update the helper_func to use this new derived class:

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2. Calling from the Helper Function

With the above changes, you can now invoke the helper_func in your test as shown below:

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Conclusion

When working with protected methods in C+ + GTest, particularly when you wish to call them from helper functions, understanding class scope and inheritance is crucial. By creating a derived class, you can extend the visibility of protected methods and use them as intended throughout your testing framework.

This not only enhances code readability and organization but also retains the encapsulation principles of object-oriented programming, allowing for cleaner and more maintainable test code.

Further Considerations

If you need to manipulate or extend the existing test fixture beyond this workaround, consider how your test framework will accommodate future changes.

Always ensure that any changes maintain the integrity and accessibility of your tests while simplifying their use.

By following these practices, you'll harness the full potential of C+ + GTest while addressing any accessibility challenges that may arise.