Clarification regarding Transaction start and end #141

Went through the spec and the test cases implemented in HID compliance seems to be very confusing.
The spec also does not talk about the transaction start and end clearly.
https://fidoalliance.org/specs/fido-u2f-HID-protocol-v1.0-rd-20141008.pdf

2.5.1 Transaction atomicity, idle- and busy states.

1. In the compliance test cases what triggers closing of the channel on the HID side ?
2. Can someone please clarify the expected behavior of the authenticator ?

Many of the compliance issues we have been facing are due to inconsistent state of the authenticator.

Thanks,
-Harsha