This method is deprecated or moved on the latest stable version.
The last existing version (v2_2_9) is shown here.
test_files=(list)
public
Explicitly define the list of test
files to be included in a test. list is expected to be an array
of file names (a FileList is acceptable).
If both pattern and test_files are used, then the list of
test files is the union of the two.
# File lib/rake/testtask.rb, line 75
def test_files=(list)
@test_files = list
end