Changes to config in GrailsUnitTestCase implementor are not reset between test methods - causing side effects

[boardbloke]

I have a Grails 5.0.x plugin project and I have noticed that in unit tests, if I change the config in a test method in order to test aspects of the class under test, then that change persists after the end of the test method - causing difficult to find side effects.

For example - consider the following test methods that test a class AClass

def 'test using configA'() {
  given:
  config.aProperty = 'A'
  expect:
    // Some behaviour of the class works as expected
    AClass.someMethod() == 'resultThatDependsOnConfigBeingA"
}

def 'test using configB'() {
  given:
  config.aProperty = 'B'

  expect:
  // Some behaviour of the class works as expected
  AClass.someMethod() == 'resultThatDependsOnConfigBeingB"
}

def 'testing something else'() {
  given:
    // config.aProperty has now been changed to 'B' for this test, because it runs later
  expect:
    // Behaviour here depends on whether this test method runs before or after the above methods - so is fragile to changes in other test methods
}

The issue appears to be that the changes to the config persist after a test method has finished, which pollutes the fixtures for all other tests in the test class.

I have managed to workaround this by calling the following in the setup() method of the test class:

config.clear()
config.refresh()

But it seems to me that ought to be the default behaviour