Ruby：TDD编码实践——如何让Minitest测试用例通过？

Let's walk through how to get your test cases passing, step by step. First, let's recap your current code and the issues you're facing:

Your Test Code #

gem 'minitest', '~> 5.2' # TDD
require 'minitest/autorun'
require 'minitest/pride'
require_relative 'kid'

class KidTest < Minitest::Test
  def test_kid_has_not_eaten_sugar
    kid = Kid.new
    assert_equal 0, kid.grams_of_sugar_eaten
  end

  def test_kid_gets_5_grams_from_eating_candy
    kid = Kid.new
    kid.eat_candy
    assert_equal 5, kid.grams_of_sugar_eaten
    5.times { kid.eat_candy }
    assert_equal 30, kid.grams_of_sugar_eaten
  end

  def test_kid_is_not_hyperactive
    kid = Kid.new
    refute kid.hyperactive?
  end

  def test_kid_is_hyperactive_after_60_grams_of_sugar
    kid = Kid.new
    11.times { kid.eat_candy }
    refute kid.hyperactive?, "Not hyperactive yet..."
    kid.eat_candy
    assert kid.hyperactive?, "OK, now the kid is hyperactive."
  end
end

Current Kid Implementation #

class Kid
  attr_reader :grams_of_sugar_eaten

  def initialize
    @grams_of_sugar_eaten = 0
  end

  def eat_candy(grams = 5)
    @grams_of_sugar_eaten += grams
  end

  def hyperactive?
    false
  end
end

Step 1: Troubleshoot the Second Test Case #

First, let's look at the test for sugar accumulation. Your eat_candy method actually looks correct—it adds 5 grams each time (with a default parameter) and updates the instance variable properly.

If this test is failing, double-check:

• Did you accidentally use = instead of += in eat_candy? (Your current code uses +=, which is right.)
• Is the attr_reader :grams_of_sugar_eaten correctly exposing the instance variable? (Yes, that's set up properly.)
• Try adding a debug puts kid.grams_of_sugar_eaten in the test to see what the actual value is at each step—this can help catch unexpected behavior.

Assuming your code is exactly as you posted, this test should pass! If it's not, a simple typo is the most likely culprit.

Step 2: Fix the Hyperactivity Test #

The big issue is the hyperactive? method—it currently always returns false, which fails the final test. Let's align it with the test requirements:

• The test expects the kid to not be hyperactive at 55 grams (11 * 5)
• The kid should become hyperactive once they hit 60 grams (12 * 5)

Update the hyperactive? method to check the accumulated sugar:

def hyperactive?
  @grams_of_sugar_eaten >= 60
end

This will return true only when the kid has eaten 60 or more grams of sugar, which matches exactly what your test expects.

Step 3: Final Working Kid Class #

Here's the revised implementation that will pass all tests:

class Kid
  attr_reader :grams_of_sugar_eaten

  def initialize
    @grams_of_sugar_eaten = 0
  end

  def eat_candy(grams = 5)
    @grams_of_sugar_eaten += grams
  end

  def hyperactive?
    @grams_of_sugar_eaten >= 60
  end
end

Run your tests again, and all cases should now pass!

内容的提问来源于stack exchange，提问作者cjl85