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I've found https://github.com/gradle/gradle/blob/3aa8e82bc5dfff2b09748c7834240741dfb7558a/subprojects/testing-jvm/src/main/java/org/gradle/api/internal/tasks/testing/detection/DefaultTestExecuter.java Which kinda answers my question, it should be single instance of this executor across modules. right?

It is an option on a task of type

Test

and thus should only affect the task you set it on.

That makes total sense, thank you!