Gradle: Can I build up multiple excludes by calling excludeCategories more than once

I know I can use the following to exclude 1 or more categories from my test run.

One Category

excludeCategories = 'my.test.Category1'

Multiple Categories

excludeCategories = 'my.test.Category1', 'my.test.Category2'

What happens if i specify the excludesCategories multiple times in my build file? Does the latter overwrite the previous?

For example is excludeCategories = 'my.test.Category1' excludeCategories = 'my.test.Category2'

The same as

excludeCategories = 'my.test.Category1', 'my.test.Category2'

Or is the result of the 2 commands that only Category2 is excluded?

Do I have to do += to add the 2nd category to the excluded list? i.e.

excludeCategories = 'my.test.Category1'
excludeCategories += 'my.test.Category2'