Ruby Minitest simple test raise error - wrong number of arguments error

Question

I'm trying to learn the TDD approach, to do so I'm using pure Ruby app which is responsible for formatting UK phone number. In my class I want to test if the whitespaces and are removed from given phone number. Basically I'm trying to test the Ruby .delete(' ') method.

Tested module

# lib/formatter/phone_number/uk.rb

module Formatter
  module PhoneNumber
    module Uk
      
      (...)

      def self.format(number)
        number.delete(' ')
      end
    end
  end
end

The test

# test/lib/formater/phone_number/uk_test.rb

require 'minitest/autorun'

class UkTest < Minitest::Test
  test 'remove whitespaces' do
    invalid_number = '+44 12 12 12 12   '
    Formatter::PhoneNumber::Uk.format(invalid_number)

    assert_equal '+4412121212'
  end
end

Which give me an error:

test/lib/formater/phone_number/uk_test.rb:6:in `test': wrong number of arguments (given 1, expected 2) (ArgumentError)

Aside from the fact that testing a method built in Ruby is not a good idea, what am I doing wrong?

@Code-Apprentice It's `test/lib/formater/phone_number/uk_test.rb:6:in test': wrong number of arguments (given 1, expected 2) (ArgumentError)` — mr_muscle, Oct 05 '21 at 22:55

knut · Accepted Answer · 2021-10-05T23:04:11.990

2

You must define a test-method (the method name must start with test_).

Inside the test method you define your assertions. In your case, you compare the expected value with the result of your method.

class UkTest < Minitest::Test
  def test_remove_whitespaces
    invalid_number = '+44 12 12 12 12   '
    assert_equal '+4412121212', Formatter::PhoneNumber::Uk.format(invalid_number)
  end
end

Full test in one file:

module Formatter
  module PhoneNumber
    module Uk
      def self.format(number)
        number.delete(' ')
      end
    end
  end
end

require 'minitest/autorun'

class UkTest < Minitest::Test
  def test_remove_whitespaces
    invalid_number = '+44 12 12 12 12   '
    assert_equal '+4412121212', Formatter::PhoneNumber::Uk.format(invalid_number)
  end
end

Same test with minitest/spec

require 'minitest/spec'
describe Formatter::PhoneNumber::Uk do
  it 'removes spaces from numbers' do
        invalid_number = '+44 12 12 12 12   '
        _(Formatter::PhoneNumber::Uk.format(invalid_number)).must_equal('+4412121212')
  end
end

edited Oct 05 '21 at 23:04

answered Oct 05 '21 at 22:17

knut

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Ok but why I can't use `test '(...)' do ` syntax ? what does it depend on? BTW your code raise an error `UkTest#test_remove_whitespaces: NameError: uninitialized constant UkTest::Formatter` – mr_muscle Oct 05 '21 at 22:22
For the error: Do you load your code in `uk_test.rb`? (Depending on your settings `require uk.rb` or `require_relative uk.rb`) - I added a full example with the complete code in one file. – knut Oct 05 '21 at 22:48
Ok I've to add this file based on a very strange way - `require_relative '../../../../lib/formatter/phone_number/uk'`, is there any workaround to avoid this stupid `../../../../` ? – mr_muscle Oct 05 '21 at 23:02
Why do you expect the `test '(...)' do` syntax should work? I may be wrong, but I never saw this syntax in combination with minitest. Maybe it would be worth for you, to take a look to rspec or minitest/spec. I will add a little code example. – knut Oct 05 '21 at 23:02
for your `require_relative`-question: It depends on you folder structure. You could also extend the loadpath `$LOAD_PATH` (see e.g. https://stackoverflow.com/questions/5177648/ruby-adding-a-directory-to-load-path-what-does-it-do). – knut Oct 05 '21 at 23:14
`test ' 'do` is standard syntax for Minitest, nothing related with `minitest/spec` https://guides.rubyonrails.org/testing.html#rails-meets-minitest check the section with `test "the truth" do `. I don't know but maybe it works only when Rails is on board - my app is pure Ruby app. – mr_muscle Oct 05 '21 at 23:17
@mr_muscle Yes, it looks like the `test '...' do ... end` syntax is an extension to minitest that Rails adds. – Code-Apprentice Oct 06 '21 at 15:52

Ruby Minitest simple test raise error - wrong number of arguments error

1 Answers1