Change TestSelector._fd_to_key from a extended copy of TestSelector._selector._fd_to_key to a view on TestSelector._selector._fd_to_key plus the test-part extension. As a result, there is no need to update TestSelector._fd_to_key when TestSelector._selector._fd_to_key is modified.
Change
TestSelector._fd_to_key
from a extended copy ofTestSelector._selector._fd_to_key
to a view onTestSelector._selector._fd_to_key
plus the test-part extension. As a result, there is no need to updateTestSelector._fd_to_key
whenTestSelector._selector._fd_to_key
is modified.fix #128