Support "expect no packets" in STF (#55)
Support "expect no packets" in STF (#55)

Specifying `expect 1` as an STF statement will tell the test runner to
expect 0 packets to appear on interface 1. Any packets that egress
interface 1 will cause an error. This is useful for test cases that
explicitly should not generate packets -- e.g. for filtering programs.
p4lang/p4app,p4lang/p4app