module Expectable

# File lib/expectable.rb, line 5
def expect(method_name, return_value = nil, expected_args = nil)
  mock = expect_helper(return_value, expected_args)

  stub(method_name, mock) do
    yield
  end

  begin
    mock.verify
  rescue
    raise ExpectationError, "Expected method #{method_name} to be called on object " \
                            "<#{self.class} ##{object_id}>"
  end
end

# File lib/expectable.rb, line 22
def expect_helper(return_value = nil, expected_args = nil)
  mock = Minitest::Mock.new

  # Expected arguments can either be an array or a Proc
  if expected_args && expected_args.is_a?(Array)
    mock.expect :call, return_value, expected_args
    # Note: In Ruby lambdas have class Proc
  elsif expected_args && expected_args.class == Proc
    mock.expect :call, return_value, &expected_args
  else
    # Allows us to run expect without caring about which args are given
    # I know that this isn't Minitest behaviour, but it's prettier
    mock.expect :call, return_value do
      true
    end
  end

  mock
end