assert_that.rb

# an assert_that method that accepts a Mocha parameter matcher
# based http://joe.truemesh.com/blog/000511.html by Joe Walnes

require 'test/unit'
require 'rubygems'
require 'mocha'

class MyTest < Test::Unit::TestCase

  def test_equals
    assert_that 2, equals(3)
  end
  
#   1) Failure:
# test_equals(MyTest)
# method assert_that in assert_that.rb at line 30
# method test_equals in assert_that.rb at line 8
# Expected: 3; Actual: 2

  def test_includes
    assert_that [5,7,9], includes(2)
  end
  
#   2) Failure:
# test_has_value(MyTest)
# method assert_that in assert_that.rb at line 30
# method test_has_value in assert_that.rb at line 16
# Expected: has_value(5); Actual: {1 => 2, 3 => 4}

  def test_has_value
    assert_that({1 => 2, 3 => 4}, has_value(5))
  end
  
#   3) Failure:
# test_includes(MyTest)
# method assert_that in assert_that.rb at line 30
# method test_includes in assert_that.rb at line 12
# Expected: includes(2); Actual: [5, 7, 9]

  def test_instance_of
    assert_that Object.new, instance_of(Array)
  end
  
#   4) Failure:
# test_instance_of(MyTest)
# method assert_that in assert_that.rb at line 30
# method test_instance_of in assert_that.rb at line 20
# Expected: instance_of(Array); Actual: #<Object:0x1238790>

  def test_regexp_matches
    assert_that "hello world", regexp_matches(/goodbye/)
  end
  
#   5) Failure:
# test_regexp_matches(MyTest)
# method assert_that in assert_that.rb at line 30
# method test_regexp_matches in assert_that.rb at line 24
# Expected: regexp_matches(/goodbye/); Actual: 'hello world'

  private

  def assert_that(actual, matcher)
    unless matcher.matches?([actual])
      message = %{Expected: #{matcher.mocha_inspect}; Actual: #{actual.mocha_inspect}}
      raise Test::Unit::AssertionFailedError.new(message)
    end
  end
end