lnwire.MilliSatoshi is now a signed integer, as a result, we’ll return
a different error if our balances go to negative due to the inability
to pay a the set fee.
Appendix C of BOLT 03 contains a series of test vectors asserting that
commitment, HTLC success, and HTLC timeout transactions are created
correctly. Here the test cases are transcribed to Go structs and
verified.
We also break out some logic need to tests that bypass the constructor
and remove some redundant fields.
