By default tests will run in system mode, i.e. without taking into account users permissions. In order to be realistic, a test needs to run Business logic code in User context. This is done by encapsulating the tested code in https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_testing_tools_runas.htm[``++System.runAs()++``].
This rule raises an issue when a test function, i.e. a function annotated with ``++@isTest++`` or ``++testMethod++``, does not contain a ``++System.runAs()++`` call.
No issue will be raised if the test class, i.e. the class annotated with ``++@isTest++``, contains helper methods, i.e. methods *not* annotated with ``++@isTest++`` or ``++testmethod++``, which contain calls to ``++System.runAs()++``. This indicates that the test code has been factorized and the rule would raise false positives.