New cop to check assert_raises with generic exceptions is followed by error message check

[fatkodima]

When testing for generic errors (like ArgumentError, RuntimeError, KeyError, IndexError etc) we need to check for the error message to not get false positives.

def foo(a, b, c)
  raise ArgumentError, "c should be 'foo'" unless c == "foo"
  # ...
end

# bad
assert_raises(ArgumentError) do
  foo(1, 2) # c is missing
end

# good
error = assert_raises(ArgumentError) do
  foo(1, 2)
end

assert_equal "c should be 'foo'", error.message # or assert_match or assert_includes

assert_raises(RuntimeError) is a 💥

[fatkodima]

@koic Wdyt on this?

[koic]

If it is disabled by default, I think it can be accepted. Probably because it is too strict as a default rule.

[koic]

This rule seems too strict to be default, and there appears to be no requests or opinions on it for about two years. Since there has been no activity for several years, I will close this. Thank you for the proposal.