Fixed tests that did not test anything.

  expect(foo) == bar

will be false because it compares with an instance of
RSpec::Expectations::ExpectationTarget
Only when we call its #to or #not_to/#to_not methods is the expectation
really checked.
Use `.to eq nil` for better output in case of mismatch.

where we will get to see the non-nil value
Made the recently fixed tests pass again.