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alexwebgr's solution

to Resistor Color in the Ruby Track

Published at Nov 30 2020 · 0 comments
Test suite

Resistors have color coded bands, where each color maps to a number. The first 2 bands of a resistor have a simple encoding scheme: each color maps to a single number.

These colors are encoded as follows:

  • Black: 0
  • Brown: 1
  • Red: 2
  • Orange: 3
  • Yellow: 4
  • Green: 5
  • Blue: 6
  • Violet: 7
  • Grey: 8
  • White: 9

Mnemonics map the colors to the numbers, that, when stored as an array, happen to map to their index in the array: Better Be Right Or Your Great Big Values Go Wrong.

More information on the color encoding of resistors can be found in the Electronic color code Wikipedia article

For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby resistor_color_test.rb

To include color from the command line:

ruby -r minitest/pride resistor_color_test.rb


Maud de Vries, Erik Schierboom https://github.com/exercism/problem-specifications/issues/1458

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


require 'minitest/autorun'
require_relative 'resistor_color'

# Common test data version: 1.0.0 edf1778
class ResistorColorTest < Minitest::Test
  def test_black
    # skip
    assert_equal 0, ResistorColor.color_code("black")

  def test_white
    assert_equal 9, ResistorColor.color_code("white")

  def test_orange
    assert_equal 3, ResistorColor.color_code("orange")

  def test_colors
    expected = ["black", "brown", "red", "orange", "yellow", "green", "blue", "violet", "grey", "white"]
    assert_equal expected, ResistorColor::COLORS
Write your code for the 'Resistor Color' exercise in this file. Make the tests in
`resistor_color_test.rb` pass.

To get started with TDD, see the `README.md` file in your
`ruby/resistor-color` directory.

class ResistorColor
  COLORS = %w[black brown red orange yellow green blue violet grey white]
  def self.color_code(color)

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