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rubyrspectestunitruby-1.8.7

Idiomatic Test::Unit equivalent of expect {}.to change {}.by(x)

Right now, I am simply using assert_equal twice - before and after the execution, and it does not hurt much. But I have used RSpec before and liked the readability of the expect{}.to change idiom. I cannot simply use RSpec in this project - not my project, not my stack.

Is there is a more idiomatic way to express an expected change/delta with Test::Unit?

Thank you.

I am working with Ruby 1.8.7

Solution

  • To accomplish assert_change with test unit, you can roll your own.

    Here's example code to get you started. Adjust it for your preferences.

    def assert_change valuer, delta, changer, message = nil
  expect = valuer.call + delta
  changer.call
  actual = valuer.call
  assert_equal expect, actual, message
end

    Usage:

    @x = 123

def foo
  @x += 456
end

assert_change(lambda{@x}, 456, lambda{foo})