module ActiveSupport::Testing::MethodCallAssertions

def assert_called_on_instance_of(klass, method_name, message = nil, times: 1, returns: nil)
  times_called = 0
  klass.define_method("stubbed_#{method_name}") do |*|
    times_called += 1
    returns
  end
  klass.alias_method "original_#{method_name}", method_name
  klass.alias_method method_name, "stubbed_#{method_name}"
  yield
  error = "Expected #{method_name} to be called #{times} times, but was called #{times_called} times"
  error = "#{message}.\n#{error}" if message
  assert_equal times, times_called, error
ensure
  klass.alias_method method_name, "original_#{method_name}"
  klass.undef_method "original_#{method_name}"
  klass.undef_method "stubbed_#{method_name}"
end