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Diego Novais
Diego Novais

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First player wins! Building the code and make the tests pass

#elixir #algorithms #webdev #tutorial

Now we'll continue to code our module Game following the tests. But this time, covering the scenario when the first player wins.

Our Game module looks like this:

# lib/game.ex defmodule Game do defmodule Game do @moduledoc """ Documentation for `Game`. """ def play(first_player_choice, second_player_choice) do result(first_player_choice, second_player_choice) end defp result(first_player_choice, second_player_choice) do cond do first_player_choice == second_player_choice -> {:ok, "Draw!"} end end end end
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With our tests done, if we run the tests now:

mix test
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We'll see the tests failures:

 1) test Game.play/2 when first player wins when first player chooses scissors and second player chooses paper (GameTest) test/game_test.exs:38 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:12: Game.result/2 test/game_test.exs:42: (test) 2) test Game.play/2 when first player wins when first player chooses stone and second player chooses scissors (GameTest) test/game_test.exs:56 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:12: Game.result/2 test/game_test.exs:60: (test) 3) test Game.play/2 when first player wins when first player chooses paper and second player chooses stone (GameTest) test/game_test.exs:47 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:12: Game.result/2 test/game_test.exs:51: (test) .. Finished in 0.03 seconds (0.00s async, 0.03s sync) 6 tests, 3 failures
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Let's make those tests pass

Now, we need to create some module attributes for stone, paper, and scissors:

defmodule Game do @moduledoc """ Documentation for `Game`. """ @stone 1 @paper 2 @scissor 3 # ... end
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And then, we'll add the condition that guarantees that the first player is the winner according to our tests.

When the first player chooses scissors and the second player chooses paper

We'll add the condition when the first player chooses scissors and the second player chooses paper:

defmodule Game do @moduledoc """ Documentation for `Game`. """ def play(first_player_choice, second_player_choice) do result(first_player_choice, second_player_choice) end defp result(first_player_choice, second_player_choice) do cond do first_player_choice == second_player_choice -> {:ok, "Draw!"} first_player_choice == @scissor && second_player_choice == @paper -> {:ok, "First player win!!!"} end end end
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And now, if we rerun the tests:

mix test
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The test with the actual scenario passed ok. And now we have just two tests with failure.

Ps.: We have one warning message about the module attributes @stone that was set but never used.

Compiling 1 file (.ex) warning: module attribute @stone was set but never used lib/game.ex:5 ... 1) test Game.play/2 when first player wins when first player chooses stone and second player chooses scissors (GameTest) test/game_test.exs:56 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:18: Game.result/2 test/game_test.exs:60: (test) . 2) test Game.play/2 when first player wins when first player chooses paper and second player chooses stone (GameTest) test/game_test.exs:47 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:18: Game.result/2 test/game_test.exs:51: (test) Finished in 0.03 seconds (0.00s async, 0.03s sync) 6 tests, 2 failures Randomized with seed 797736 ... Finished in 0.02 seconds (0.00s async, 0.02s sync) 3 tests, 0 failures Randomized with seed 352470
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When the first player chooses paper and the second player chooses stone

  • We'll add the condition when the first player chooses paper and the second player chooses stone: 
defmodule Game do @moduledoc """ Documentation for `Game`. """ def play(first_player_choice, second_player_choice) do result(first_player_choice, second_player_choice) end defp result(first_player_choice, second_player_choice) do cond do first_player_choice == second_player_choice -> {:ok, "Draw!"} first_player_choice == @scissor && second_player_choice == @paper -> {:ok, "First player win!!!"} first_player_choice == @paper && second_player_choice == @stone -> {:ok, "First player win!!!"} end end end
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And now, if we rerun the tests:

mix test
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The test with the actual scenario passed ok. And now we have just one tests with failure.

Compiling 1 file (.ex) .. 1) test Game.play/2 when first player wins when first player chooses stone and second player chooses scissors (GameTest) test/game_test.exs:56 ** (CondClauseError) no cond clause evaluated to a truthy value code: assert {:ok, match} = Game.play(first_player_choice, second_player_choise) stacktrace: (rock_paper_scissor_elixir 0.1.0) lib/game.ex:21: Game.result/2 test/game_test.exs:60: (test) ... Finished in 0.03 seconds (0.00s async, 0.03s sync) 6 tests, 1 failure Randomized with seed 450094
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When the first player chooses stone and the second player chooses scissors

  • We'll add the condition when the first player chooses stone and the second player chooses scissors: 
defmodule Game do @moduledoc """ Documentation for `Game`. """ def play(first_player_choice, second_player_choice) do result(first_player_choice, second_player_choice) end defp result(first_player_choice, second_player_choice) do cond do first_player_choice == second_player_choice -> {:ok, "Draw!"} first_player_choice == @scissor && second_player_choice == @paper -> {:ok, "First player win!!!"} first_player_choice == @paper && second_player_choice == @stone -> {:ok, "First player win!!!"} first_player_choice == @stone && second_player_choice == @scissor -> {:ok, "First player win!!!"} end end end
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And now, if we rerun the tests:

mix test
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All the tests pass with success.

Compiling 1 file (.ex) ...... Finished in 0.03 seconds (0.00s async, 0.03s sync) 6 tests, 0 failures Randomized with seed 795123
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In the next post, we'll build the tests covering the scenario when the second player wins.

Contacts

Email: contato@diegonovais.com.br
Linkedin: https://www.linkedin.com/in/diegonovais/
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