Increase test coverage for checkerMain.ml

[gkaracha]

These unit tests primarily go through different execution paths and ensure that calls to entrypoints fail/succeed, depending on whether checker is sealed/unsealed. However, the values themselves are not inspected.

At this high a level most of the actual code to be run is wrapped in {BEGIN,END}_LIGO, so I think e2e tests are much more appropriate for testing the behavior of main.

Test coverage goes from 86.40% to 88.52%.

[gkaracha]

Thanks for the review @dorranh! Indeed, I made two changes for coverage purposes:

• Moved the right-hand side of this clause to the same line as the pattern:

• | CheckerEntrypoint _ ->

• (Ligo.failwith error_ContractNotDeployed: LigoOp.operation list lazy_function_map (string, Ligo.bytes) Ligo.big_map * deployment_state)

• | CheckerEntrypoint _ -> (Ligo.failwith error_ContractNotDeployed: LigoOp.operation list lazy_function_map (string, Ligo.bytes) Ligo.big_map * deployment_state)

  
  This at least makes the coverage report to mark the line as yellow (pattern: green, rhs: red due to https://github.com/aantron/bisect_ppx/issues/377), which I can read as green (if the pattern is matched, then the rhs is trivially accessed).

• Switched the if-then-else for a match-with, as you pointed out. I've noticed that the else is never marked red or green, so, to get the "yellow" behavior I mentioned in the previous point, I switched to pattern matching instead.

Overall, since I don't expect https://github.com/aantron/bisect_ppx/issues/377 to be changed any time soon I've been thinking that we can combine @aantron's advice with using pattern matches instead of if-then-else to get accurate coverage. That is, if we convert

if <condition>
then e1
else (Ligo.failwith (...))

into

match <condition> with
| true -> e1
| false -> ((Ligo.failwith [@coverage off]) (...))        (* tricky *)

then the "tricky" line is colored green when covered by the tests and red when not covered by the tests, as we want.