[shoulda-matchers gem] validate_numericality_of_matcher strange behaviour

Hello
I have Vacancy model and vacancy_spec test with validates_numericality_of :salary, greater_than: 1 in the model and
validate_numericality_of(:salary).is_greater_than(2) in the _spec.
When i run rspec spec command tests pass (in some cases and in other they don’t)
Why?

vacancy.rb