c84c2b8c92 tests: Test for expected return values when calling functions returning a success code (practicalswift)
Pull request description:
Test for expected return values when calling functions returning a success code (instead of discarding the return values).
**Note to reviewers:** The following commands can be used to verify that the only text fragments added in this PR are `BOOST_CHECK(`, `!` and `)` :
```
$ git diff HEAD~1 | grep -E '^[\-][^\-]' | cut -b2- > before.txt
$ git diff HEAD~1 | grep -E '^[\+][^\+]' | cut -b2- > after.txt
$ cat after.txt | sed 's/BOOST_CHECK(//g' | sed 's/));/);/g' | tr -d '!' > after-sed.txt
$ diff -u before.txt after-sed.txt
$
```
Tree-SHA512: ff0863ef2046a2eda3c44e9c6b9aedfe167881f2fa58db29fef859416831233ef6502a3a11fd2322bc1a924db83df8d4a5c5879298007f2a7b085e2a7286af70
This trivial change adds the "override" keyword to some methods of
subclasses meant to override interface methods. This ensures that any
future change to the interface' method signatures which are not correctly
mirrored in the subclass will break at compile time with a clear error message,
rather than fail at runtime (which is harder to debug).
After a recent bug discovered in callback ordering in MainSignals,
this test checks invariants in ordering of
BlockConnected / BlockDisconnected / UpdatedChainTip signals
