angelikatyborska's solution to Beer Song on the Elixir track

Instructions

Test suite

Solution

Recite the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.

Note that not all verses are identical.

99 bottles of beer on the wall, 99 bottles of beer.
Take one down and pass it around, 98 bottles of beer on the wall.

98 bottles of beer on the wall, 98 bottles of beer.
Take one down and pass it around, 97 bottles of beer on the wall.

97 bottles of beer on the wall, 97 bottles of beer.
Take one down and pass it around, 96 bottles of beer on the wall.

96 bottles of beer on the wall, 96 bottles of beer.
Take one down and pass it around, 95 bottles of beer on the wall.

95 bottles of beer on the wall, 95 bottles of beer.
Take one down and pass it around, 94 bottles of beer on the wall.

94 bottles of beer on the wall, 94 bottles of beer.
Take one down and pass it around, 93 bottles of beer on the wall.

93 bottles of beer on the wall, 93 bottles of beer.
Take one down and pass it around, 92 bottles of beer on the wall.

92 bottles of beer on the wall, 92 bottles of beer.
Take one down and pass it around, 91 bottles of beer on the wall.

91 bottles of beer on the wall, 91 bottles of beer.
Take one down and pass it around, 90 bottles of beer on the wall.

90 bottles of beer on the wall, 90 bottles of beer.
Take one down and pass it around, 89 bottles of beer on the wall.

89 bottles of beer on the wall, 89 bottles of beer.
Take one down and pass it around, 88 bottles of beer on the wall.

88 bottles of beer on the wall, 88 bottles of beer.
Take one down and pass it around, 87 bottles of beer on the wall.

87 bottles of beer on the wall, 87 bottles of beer.
Take one down and pass it around, 86 bottles of beer on the wall.

86 bottles of beer on the wall, 86 bottles of beer.
Take one down and pass it around, 85 bottles of beer on the wall.

85 bottles of beer on the wall, 85 bottles of beer.
Take one down and pass it around, 84 bottles of beer on the wall.

84 bottles of beer on the wall, 84 bottles of beer.
Take one down and pass it around, 83 bottles of beer on the wall.

83 bottles of beer on the wall, 83 bottles of beer.
Take one down and pass it around, 82 bottles of beer on the wall.

82 bottles of beer on the wall, 82 bottles of beer.
Take one down and pass it around, 81 bottles of beer on the wall.

81 bottles of beer on the wall, 81 bottles of beer.
Take one down and pass it around, 80 bottles of beer on the wall.

80 bottles of beer on the wall, 80 bottles of beer.
Take one down and pass it around, 79 bottles of beer on the wall.

79 bottles of beer on the wall, 79 bottles of beer.
Take one down and pass it around, 78 bottles of beer on the wall.

78 bottles of beer on the wall, 78 bottles of beer.
Take one down and pass it around, 77 bottles of beer on the wall.

77 bottles of beer on the wall, 77 bottles of beer.
Take one down and pass it around, 76 bottles of beer on the wall.

76 bottles of beer on the wall, 76 bottles of beer.
Take one down and pass it around, 75 bottles of beer on the wall.

75 bottles of beer on the wall, 75 bottles of beer.
Take one down and pass it around, 74 bottles of beer on the wall.

74 bottles of beer on the wall, 74 bottles of beer.
Take one down and pass it around, 73 bottles of beer on the wall.

73 bottles of beer on the wall, 73 bottles of beer.
Take one down and pass it around, 72 bottles of beer on the wall.

72 bottles of beer on the wall, 72 bottles of beer.
Take one down and pass it around, 71 bottles of beer on the wall.

71 bottles of beer on the wall, 71 bottles of beer.
Take one down and pass it around, 70 bottles of beer on the wall.

70 bottles of beer on the wall, 70 bottles of beer.
Take one down and pass it around, 69 bottles of beer on the wall.

69 bottles of beer on the wall, 69 bottles of beer.
Take one down and pass it around, 68 bottles of beer on the wall.

68 bottles of beer on the wall, 68 bottles of beer.
Take one down and pass it around, 67 bottles of beer on the wall.

67 bottles of beer on the wall, 67 bottles of beer.
Take one down and pass it around, 66 bottles of beer on the wall.

66 bottles of beer on the wall, 66 bottles of beer.
Take one down and pass it around, 65 bottles of beer on the wall.

65 bottles of beer on the wall, 65 bottles of beer.
Take one down and pass it around, 64 bottles of beer on the wall.

64 bottles of beer on the wall, 64 bottles of beer.
Take one down and pass it around, 63 bottles of beer on the wall.

63 bottles of beer on the wall, 63 bottles of beer.
Take one down and pass it around, 62 bottles of beer on the wall.

62 bottles of beer on the wall, 62 bottles of beer.
Take one down and pass it around, 61 bottles of beer on the wall.

61 bottles of beer on the wall, 61 bottles of beer.
Take one down and pass it around, 60 bottles of beer on the wall.

60 bottles of beer on the wall, 60 bottles of beer.
Take one down and pass it around, 59 bottles of beer on the wall.

59 bottles of beer on the wall, 59 bottles of beer.
Take one down and pass it around, 58 bottles of beer on the wall.

58 bottles of beer on the wall, 58 bottles of beer.
Take one down and pass it around, 57 bottles of beer on the wall.

57 bottles of beer on the wall, 57 bottles of beer.
Take one down and pass it around, 56 bottles of beer on the wall.

56 bottles of beer on the wall, 56 bottles of beer.
Take one down and pass it around, 55 bottles of beer on the wall.

55 bottles of beer on the wall, 55 bottles of beer.
Take one down and pass it around, 54 bottles of beer on the wall.

54 bottles of beer on the wall, 54 bottles of beer.
Take one down and pass it around, 53 bottles of beer on the wall.

53 bottles of beer on the wall, 53 bottles of beer.
Take one down and pass it around, 52 bottles of beer on the wall.

52 bottles of beer on the wall, 52 bottles of beer.
Take one down and pass it around, 51 bottles of beer on the wall.

51 bottles of beer on the wall, 51 bottles of beer.
Take one down and pass it around, 50 bottles of beer on the wall.

50 bottles of beer on the wall, 50 bottles of beer.
Take one down and pass it around, 49 bottles of beer on the wall.

49 bottles of beer on the wall, 49 bottles of beer.
Take one down and pass it around, 48 bottles of beer on the wall.

48 bottles of beer on the wall, 48 bottles of beer.
Take one down and pass it around, 47 bottles of beer on the wall.

47 bottles of beer on the wall, 47 bottles of beer.
Take one down and pass it around, 46 bottles of beer on the wall.

46 bottles of beer on the wall, 46 bottles of beer.
Take one down and pass it around, 45 bottles of beer on the wall.

45 bottles of beer on the wall, 45 bottles of beer.
Take one down and pass it around, 44 bottles of beer on the wall.

44 bottles of beer on the wall, 44 bottles of beer.
Take one down and pass it around, 43 bottles of beer on the wall.

43 bottles of beer on the wall, 43 bottles of beer.
Take one down and pass it around, 42 bottles of beer on the wall.

42 bottles of beer on the wall, 42 bottles of beer.
Take one down and pass it around, 41 bottles of beer on the wall.

41 bottles of beer on the wall, 41 bottles of beer.
Take one down and pass it around, 40 bottles of beer on the wall.

40 bottles of beer on the wall, 40 bottles of beer.
Take one down and pass it around, 39 bottles of beer on the wall.

39 bottles of beer on the wall, 39 bottles of beer.
Take one down and pass it around, 38 bottles of beer on the wall.

38 bottles of beer on the wall, 38 bottles of beer.
Take one down and pass it around, 37 bottles of beer on the wall.

37 bottles of beer on the wall, 37 bottles of beer.
Take one down and pass it around, 36 bottles of beer on the wall.

36 bottles of beer on the wall, 36 bottles of beer.
Take one down and pass it around, 35 bottles of beer on the wall.

35 bottles of beer on the wall, 35 bottles of beer.
Take one down and pass it around, 34 bottles of beer on the wall.

34 bottles of beer on the wall, 34 bottles of beer.
Take one down and pass it around, 33 bottles of beer on the wall.

33 bottles of beer on the wall, 33 bottles of beer.
Take one down and pass it around, 32 bottles of beer on the wall.

32 bottles of beer on the wall, 32 bottles of beer.
Take one down and pass it around, 31 bottles of beer on the wall.

31 bottles of beer on the wall, 31 bottles of beer.
Take one down and pass it around, 30 bottles of beer on the wall.

30 bottles of beer on the wall, 30 bottles of beer.
Take one down and pass it around, 29 bottles of beer on the wall.

29 bottles of beer on the wall, 29 bottles of beer.
Take one down and pass it around, 28 bottles of beer on the wall.

28 bottles of beer on the wall, 28 bottles of beer.
Take one down and pass it around, 27 bottles of beer on the wall.

27 bottles of beer on the wall, 27 bottles of beer.
Take one down and pass it around, 26 bottles of beer on the wall.

26 bottles of beer on the wall, 26 bottles of beer.
Take one down and pass it around, 25 bottles of beer on the wall.

25 bottles of beer on the wall, 25 bottles of beer.
Take one down and pass it around, 24 bottles of beer on the wall.

24 bottles of beer on the wall, 24 bottles of beer.
Take one down and pass it around, 23 bottles of beer on the wall.

23 bottles of beer on the wall, 23 bottles of beer.
Take one down and pass it around, 22 bottles of beer on the wall.

22 bottles of beer on the wall, 22 bottles of beer.
Take one down and pass it around, 21 bottles of beer on the wall.

21 bottles of beer on the wall, 21 bottles of beer.
Take one down and pass it around, 20 bottles of beer on the wall.

20 bottles of beer on the wall, 20 bottles of beer.
Take one down and pass it around, 19 bottles of beer on the wall.

19 bottles of beer on the wall, 19 bottles of beer.
Take one down and pass it around, 18 bottles of beer on the wall.

18 bottles of beer on the wall, 18 bottles of beer.
Take one down and pass it around, 17 bottles of beer on the wall.

17 bottles of beer on the wall, 17 bottles of beer.
Take one down and pass it around, 16 bottles of beer on the wall.

16 bottles of beer on the wall, 16 bottles of beer.
Take one down and pass it around, 15 bottles of beer on the wall.

15 bottles of beer on the wall, 15 bottles of beer.
Take one down and pass it around, 14 bottles of beer on the wall.

14 bottles of beer on the wall, 14 bottles of beer.
Take one down and pass it around, 13 bottles of beer on the wall.

13 bottles of beer on the wall, 13 bottles of beer.
Take one down and pass it around, 12 bottles of beer on the wall.

12 bottles of beer on the wall, 12 bottles of beer.
Take one down and pass it around, 11 bottles of beer on the wall.

11 bottles of beer on the wall, 11 bottles of beer.
Take one down and pass it around, 10 bottles of beer on the wall.

10 bottles of beer on the wall, 10 bottles of beer.
Take one down and pass it around, 9 bottles of beer on the wall.

9 bottles of beer on the wall, 9 bottles of beer.
Take one down and pass it around, 8 bottles of beer on the wall.

8 bottles of beer on the wall, 8 bottles of beer.
Take one down and pass it around, 7 bottles of beer on the wall.

7 bottles of beer on the wall, 7 bottles of beer.
Take one down and pass it around, 6 bottles of beer on the wall.

6 bottles of beer on the wall, 6 bottles of beer.
Take one down and pass it around, 5 bottles of beer on the wall.

5 bottles of beer on the wall, 5 bottles of beer.
Take one down and pass it around, 4 bottles of beer on the wall.

4 bottles of beer on the wall, 4 bottles of beer.
Take one down and pass it around, 3 bottles of beer on the wall.

3 bottles of beer on the wall, 3 bottles of beer.
Take one down and pass it around, 2 bottles of beer on the wall.

2 bottles of beer on the wall, 2 bottles of beer.
Take one down and pass it around, 1 bottle of beer on the wall.

1 bottle of beer on the wall, 1 bottle of beer.
Take it down and pass it around, no more bottles of beer on the wall.

No more bottles of beer on the wall, no more bottles of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.

For bonus points

Did you get the tests passing and the code clean? If you want to, these are some additional things you could try:

Remove as much duplication as you possibly can.
Optimize for readability, even if it means introducing duplication.
If you've removed all the duplication, do you have a lot of conditionals? Try replacing the conditionals with polymorphism, if it applies in this language. How readable is it?

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

Running tests

Execute the tests with:

$ mix test

Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

Source

Learn to Program by Chris Pine http://pine.fm/LearnToProgram/?Chapter=06

Submitting Incomplete Solutions

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

beer_song_test.exs

defmodule BeerSongTest do
  use ExUnit.Case

  describe "verse" do
    # @tag :pending
    test "first generic verse" do
      assert BeerSong.verse(99) == """
             99 bottles of beer on the wall, 99 bottles of beer.
             Take one down and pass it around, 98 bottles of beer on the wall.
             """
    end

    @tag :pending
    test "last generic verse" do
      assert BeerSong.verse(3) == """
             3 bottles of beer on the wall, 3 bottles of beer.
             Take one down and pass it around, 2 bottles of beer on the wall.
             """
    end

    @tag :pending
    test "verse with 2 bottles" do
      assert BeerSong.verse(2) == """
             2 bottles of beer on the wall, 2 bottles of beer.
             Take one down and pass it around, 1 bottle of beer on the wall.
             """
    end

    @tag :pending
    test "verse with 1 bottle" do
      assert BeerSong.verse(1) == """
             1 bottle of beer on the wall, 1 bottle of beer.
             Take it down and pass it around, no more bottles of beer on the wall.
             """
    end

    @tag :pending
    test "verse with 0 bottles" do
      assert BeerSong.verse(0) == """
             No more bottles of beer on the wall, no more bottles of beer.
             Go to the store and buy some more, 99 bottles of beer on the wall.
             """
    end
  end

  describe "lyrics" do
    @tag :pending
    test "first two verses" do
      assert BeerSong.lyrics(99..98) == """
             99 bottles of beer on the wall, 99 bottles of beer.
             Take one down and pass it around, 98 bottles of beer on the wall.

             98 bottles of beer on the wall, 98 bottles of beer.
             Take one down and pass it around, 97 bottles of beer on the wall.
             """
    end

    @tag :pending
    test "last three verses" do
      assert BeerSong.lyrics(2..0) == """
             2 bottles of beer on the wall, 2 bottles of beer.
             Take one down and pass it around, 1 bottle of beer on the wall.

             1 bottle of beer on the wall, 1 bottle of beer.
             Take it down and pass it around, no more bottles of beer on the wall.

             No more bottles of beer on the wall, no more bottles of beer.
             Go to the store and buy some more, 99 bottles of beer on the wall.
             """
    end

    @tag :pending
    test "all verses" do
      assert BeerSong.lyrics() == """
             99 bottles of beer on the wall, 99 bottles of beer.
             Take one down and pass it around, 98 bottles of beer on the wall.

             98 bottles of beer on the wall, 98 bottles of beer.
             Take one down and pass it around, 97 bottles of beer on the wall.

             97 bottles of beer on the wall, 97 bottles of beer.
             Take one down and pass it around, 96 bottles of beer on the wall.

             96 bottles of beer on the wall, 96 bottles of beer.
             Take one down and pass it around, 95 bottles of beer on the wall.

             95 bottles of beer on the wall, 95 bottles of beer.
             Take one down and pass it around, 94 bottles of beer on the wall.

             94 bottles of beer on the wall, 94 bottles of beer.
             Take one down and pass it around, 93 bottles of beer on the wall.

             93 bottles of beer on the wall, 93 bottles of beer.
             Take one down and pass it around, 92 bottles of beer on the wall.

             92 bottles of beer on the wall, 92 bottles of beer.
             Take one down and pass it around, 91 bottles of beer on the wall.

             91 bottles of beer on the wall, 91 bottles of beer.
             Take one down and pass it around, 90 bottles of beer on the wall.

             90 bottles of beer on the wall, 90 bottles of beer.
             Take one down and pass it around, 89 bottles of beer on the wall.

             89 bottles of beer on the wall, 89 bottles of beer.
             Take one down and pass it around, 88 bottles of beer on the wall.

             88 bottles of beer on the wall, 88 bottles of beer.
             Take one down and pass it around, 87 bottles of beer on the wall.

             87 bottles of beer on the wall, 87 bottles of beer.
             Take one down and pass it around, 86 bottles of beer on the wall.

             86 bottles of beer on the wall, 86 bottles of beer.
             Take one down and pass it around, 85 bottles of beer on the wall.

             85 bottles of beer on the wall, 85 bottles of beer.
             Take one down and pass it around, 84 bottles of beer on the wall.

             84 bottles of beer on the wall, 84 bottles of beer.
             Take one down and pass it around, 83 bottles of beer on the wall.

             83 bottles of beer on the wall, 83 bottles of beer.
             Take one down and pass it around, 82 bottles of beer on the wall.

             82 bottles of beer on the wall, 82 bottles of beer.
             Take one down and pass it around, 81 bottles of beer on the wall.

             81 bottles of beer on the wall, 81 bottles of beer.
             Take one down and pass it around, 80 bottles of beer on the wall.

             80 bottles of beer on the wall, 80 bottles of beer.
             Take one down and pass it around, 79 bottles of beer on the wall.

             79 bottles of beer on the wall, 79 bottles of beer.
             Take one down and pass it around, 78 bottles of beer on the wall.

             78 bottles of beer on the wall, 78 bottles of beer.
             Take one down and pass it around, 77 bottles of beer on the wall.

             77 bottles of beer on the wall, 77 bottles of beer.
             Take one down and pass it around, 76 bottles of beer on the wall.

             76 bottles of beer on the wall, 76 bottles of beer.
             Take one down and pass it around, 75 bottles of beer on the wall.

             75 bottles of beer on the wall, 75 bottles of beer.
             Take one down and pass it around, 74 bottles of beer on the wall.

             74 bottles of beer on the wall, 74 bottles of beer.
             Take one down and pass it around, 73 bottles of beer on the wall.

             73 bottles of beer on the wall, 73 bottles of beer.
             Take one down and pass it around, 72 bottles of beer on the wall.

             72 bottles of beer on the wall, 72 bottles of beer.
             Take one down and pass it around, 71 bottles of beer on the wall.

             71 bottles of beer on the wall, 71 bottles of beer.
             Take one down and pass it around, 70 bottles of beer on the wall.

             70 bottles of beer on the wall, 70 bottles of beer.
             Take one down and pass it around, 69 bottles of beer on the wall.

             69 bottles of beer on the wall, 69 bottles of beer.
             Take one down and pass it around, 68 bottles of beer on the wall.

             68 bottles of beer on the wall, 68 bottles of beer.
             Take one down and pass it around, 67 bottles of beer on the wall.

             67 bottles of beer on the wall, 67 bottles of beer.
             Take one down and pass it around, 66 bottles of beer on the wall.

             66 bottles of beer on the wall, 66 bottles of beer.
             Take one down and pass it around, 65 bottles of beer on the wall.

             65 bottles of beer on the wall, 65 bottles of beer.
             Take one down and pass it around, 64 bottles of beer on the wall.

             64 bottles of beer on the wall, 64 bottles of beer.
             Take one down and pass it around, 63 bottles of beer on the wall.

             63 bottles of beer on the wall, 63 bottles of beer.
             Take one down and pass it around, 62 bottles of beer on the wall.

             62 bottles of beer on the wall, 62 bottles of beer.
             Take one down and pass it around, 61 bottles of beer on the wall.

             61 bottles of beer on the wall, 61 bottles of beer.
             Take one down and pass it around, 60 bottles of beer on the wall.

             60 bottles of beer on the wall, 60 bottles of beer.
             Take one down and pass it around, 59 bottles of beer on the wall.

             59 bottles of beer on the wall, 59 bottles of beer.
             Take one down and pass it around, 58 bottles of beer on the wall.

             58 bottles of beer on the wall, 58 bottles of beer.
             Take one down and pass it around, 57 bottles of beer on the wall.

             57 bottles of beer on the wall, 57 bottles of beer.
             Take one down and pass it around, 56 bottles of beer on the wall.

             56 bottles of beer on the wall, 56 bottles of beer.
             Take one down and pass it around, 55 bottles of beer on the wall.

             55 bottles of beer on the wall, 55 bottles of beer.
             Take one down and pass it around, 54 bottles of beer on the wall.

             54 bottles of beer on the wall, 54 bottles of beer.
             Take one down and pass it around, 53 bottles of beer on the wall.

             53 bottles of beer on the wall, 53 bottles of beer.
             Take one down and pass it around, 52 bottles of beer on the wall.

             52 bottles of beer on the wall, 52 bottles of beer.
             Take one down and pass it around, 51 bottles of beer on the wall.

             51 bottles of beer on the wall, 51 bottles of beer.
             Take one down and pass it around, 50 bottles of beer on the wall.

             50 bottles of beer on the wall, 50 bottles of beer.
             Take one down and pass it around, 49 bottles of beer on the wall.

             49 bottles of beer on the wall, 49 bottles of beer.
             Take one down and pass it around, 48 bottles of beer on the wall.

             48 bottles of beer on the wall, 48 bottles of beer.
             Take one down and pass it around, 47 bottles of beer on the wall.

             47 bottles of beer on the wall, 47 bottles of beer.
             Take one down and pass it around, 46 bottles of beer on the wall.

             46 bottles of beer on the wall, 46 bottles of beer.
             Take one down and pass it around, 45 bottles of beer on the wall.

             45 bottles of beer on the wall, 45 bottles of beer.
             Take one down and pass it around, 44 bottles of beer on the wall.

             44 bottles of beer on the wall, 44 bottles of beer.
             Take one down and pass it around, 43 bottles of beer on the wall.

             43 bottles of beer on the wall, 43 bottles of beer.
             Take one down and pass it around, 42 bottles of beer on the wall.

             42 bottles of beer on the wall, 42 bottles of beer.
             Take one down and pass it around, 41 bottles of beer on the wall.

             41 bottles of beer on the wall, 41 bottles of beer.
             Take one down and pass it around, 40 bottles of beer on the wall.

             40 bottles of beer on the wall, 40 bottles of beer.
             Take one down and pass it around, 39 bottles of beer on the wall.

             39 bottles of beer on the wall, 39 bottles of beer.
             Take one down and pass it around, 38 bottles of beer on the wall.

             38 bottles of beer on the wall, 38 bottles of beer.
             Take one down and pass it around, 37 bottles of beer on the wall.

             37 bottles of beer on the wall, 37 bottles of beer.
             Take one down and pass it around, 36 bottles of beer on the wall.

             36 bottles of beer on the wall, 36 bottles of beer.
             Take one down and pass it around, 35 bottles of beer on the wall.

             35 bottles of beer on the wall, 35 bottles of beer.
             Take one down and pass it around, 34 bottles of beer on the wall.

             34 bottles of beer on the wall, 34 bottles of beer.
             Take one down and pass it around, 33 bottles of beer on the wall.

             33 bottles of beer on the wall, 33 bottles of beer.
             Take one down and pass it around, 32 bottles of beer on the wall.

             32 bottles of beer on the wall, 32 bottles of beer.
             Take one down and pass it around, 31 bottles of beer on the wall.

             31 bottles of beer on the wall, 31 bottles of beer.
             Take one down and pass it around, 30 bottles of beer on the wall.

             30 bottles of beer on the wall, 30 bottles of beer.
             Take one down and pass it around, 29 bottles of beer on the wall.

             29 bottles of beer on the wall, 29 bottles of beer.
             Take one down and pass it around, 28 bottles of beer on the wall.

             28 bottles of beer on the wall, 28 bottles of beer.
             Take one down and pass it around, 27 bottles of beer on the wall.

             27 bottles of beer on the wall, 27 bottles of beer.
             Take one down and pass it around, 26 bottles of beer on the wall.

             26 bottles of beer on the wall, 26 bottles of beer.
             Take one down and pass it around, 25 bottles of beer on the wall.

             25 bottles of beer on the wall, 25 bottles of beer.
             Take one down and pass it around, 24 bottles of beer on the wall.

             24 bottles of beer on the wall, 24 bottles of beer.
             Take one down and pass it around, 23 bottles of beer on the wall.

             23 bottles of beer on the wall, 23 bottles of beer.
             Take one down and pass it around, 22 bottles of beer on the wall.

             22 bottles of beer on the wall, 22 bottles of beer.
             Take one down and pass it around, 21 bottles of beer on the wall.

             21 bottles of beer on the wall, 21 bottles of beer.
             Take one down and pass it around, 20 bottles of beer on the wall.

             20 bottles of beer on the wall, 20 bottles of beer.
             Take one down and pass it around, 19 bottles of beer on the wall.

             19 bottles of beer on the wall, 19 bottles of beer.
             Take one down and pass it around, 18 bottles of beer on the wall.

             18 bottles of beer on the wall, 18 bottles of beer.
             Take one down and pass it around, 17 bottles of beer on the wall.

             17 bottles of beer on the wall, 17 bottles of beer.
             Take one down and pass it around, 16 bottles of beer on the wall.

             16 bottles of beer on the wall, 16 bottles of beer.
             Take one down and pass it around, 15 bottles of beer on the wall.

             15 bottles of beer on the wall, 15 bottles of beer.
             Take one down and pass it around, 14 bottles of beer on the wall.

             14 bottles of beer on the wall, 14 bottles of beer.
             Take one down and pass it around, 13 bottles of beer on the wall.

             13 bottles of beer on the wall, 13 bottles of beer.
             Take one down and pass it around, 12 bottles of beer on the wall.

             12 bottles of beer on the wall, 12 bottles of beer.
             Take one down and pass it around, 11 bottles of beer on the wall.

             11 bottles of beer on the wall, 11 bottles of beer.
             Take one down and pass it around, 10 bottles of beer on the wall.

             10 bottles of beer on the wall, 10 bottles of beer.
             Take one down and pass it around, 9 bottles of beer on the wall.

             9 bottles of beer on the wall, 9 bottles of beer.
             Take one down and pass it around, 8 bottles of beer on the wall.

             8 bottles of beer on the wall, 8 bottles of beer.
             Take one down and pass it around, 7 bottles of beer on the wall.

             7 bottles of beer on the wall, 7 bottles of beer.
             Take one down and pass it around, 6 bottles of beer on the wall.

             6 bottles of beer on the wall, 6 bottles of beer.
             Take one down and pass it around, 5 bottles of beer on the wall.

             5 bottles of beer on the wall, 5 bottles of beer.
             Take one down and pass it around, 4 bottles of beer on the wall.

             4 bottles of beer on the wall, 4 bottles of beer.
             Take one down and pass it around, 3 bottles of beer on the wall.

             3 bottles of beer on the wall, 3 bottles of beer.
             Take one down and pass it around, 2 bottles of beer on the wall.

             2 bottles of beer on the wall, 2 bottles of beer.
             Take one down and pass it around, 1 bottle of beer on the wall.

             1 bottle of beer on the wall, 1 bottle of beer.
             Take it down and pass it around, no more bottles of beer on the wall.

             No more bottles of beer on the wall, no more bottles of beer.
             Go to the store and buy some more, 99 bottles of beer on the wall.
             """
    end
  end
end

test_helper.exs

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)

defmodule BeerSong do
  @max 99

  @doc """
  Get a single verse of the beer song
  """
  @spec verse(integer) :: String.t()
  def verse(number) do
    """
    #{String.capitalize(first_line(number))}
    #{String.capitalize(second_line(number))}
    """
  end

  @doc """
  Get the entire beer song for a given range of numbers of bottles.
  """
  @spec lyrics(Range.t()) :: String.t()
  def lyrics(range \\ @max..0) do
    Enum.map_join(range, "\n", &verse/1)
  end

  defp first_line(number) do
    "#{bottles(number)} of beer on the wall, #{bottles(number)} of beer."
  end

  defp second_line(number) do
    "#{second_line_action(number)}, #{bottles(next(number))} of beer on the wall."
  end

  defp second_line_action(0), do: "go to the store and buy some more"
  defp second_line_action(1), do: "take it down and pass it around"
  defp second_line_action(_), do: "take one down and pass it around"

  defp bottles(0), do: "no more bottles"
  defp bottles(1), do: "1 bottle"
  defp bottles(number), do: "#{number} bottles"

  defp next(0), do: @max
  defp next(n), do: n - 1
end

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angelikatyborska's solution

to Beer Song in the Elixir Track