JUnit5 is more tolerant regarding the visibility of test classes and methods than JUnit4, which required everything to be `public`.
Test classes and methods can have any visibility except `private`.
It is however recommended to use the default package visibility to improve readability.
[quote, JUnit5 User Guide]
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Test classes, test methods, and lifecycle methods are not required to be `public`, but they must not be `private`.
It is generally recommended to omit the public modifier for test classes, test methods, and lifecycle methods unless there is a technical reason for doing so – for example, when a test class is extended by a test class in another package.
Another technical reason for making classes and methods public is to simplify testing on the module path when using the Java Module System.
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=== What is the potential impact?
The code will be non-conventional and readability can be slightly affected.
=== Exceptions
This rule does not raise an issue when the visibility is set to `private`, because `private` test methods and classes are systematically ignored by JUnit5, without a proper warning.
In this case, there is also an impact on reliability and so it is handled by the rule https://rules.sonarsource.com/java/RSPEC-5810/[S5810].