在rspec中测试递归IO提示

Question

我正在写一个connect-four游戏，以获得更多的OO和rspec练习。作为我的程序的一部分，我想提示用户选择他们想要放入游戏棋子的列。以下是该方法：

def get_col_choice(input, output)
     output.print "Player #{@player}, choose a column from 0-6: " 
     input_string = input.gets.chomp
     begin
         col_choice = Integer(input_string)
         raise("The column you chose is out of bounds.") if out_of_bounds?(col_choice)
         raise("The column you chose is fully occupied.") if unavailable?(col_choice)
         return col_choice
     rescue TypeError, ArgumentError
         output.puts "Your choice of column is invalid. Try again."
     rescue RuntimeError => err
         puts err.message
     end
     get_col_choice(input, output)
end

在IRB中，一切都按我的计划工作。我的问题是在rspec中遇到了一个NoMethodError，我认为它来自于我对get_col_choice的递归调用。

有没有人能告诉我，我可以做些什么来改进get_col_choice或者在Rspec中编写正确的测试？下面是我的控制台从我的rspec文件输出的内容：

Failures:

1) ConnectFourGame#get_col_choice notifies users which player gets to choose a column
 Failure/Error: $connect_four.get_col_choice(input, output)

 NoMethodError:
   undefined method `chomp' for nil:NilClass
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:31:in `get_col_choice'
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:42:in `get_col_choice'
 # ./connect_four_game_spec.rb:52:in `block (3 levels) in <top (required)>'

2) ConnectFourGame#get_col_choice returns the player's column choice
 Failure/Error: expect($connect_four.get_col_choice(input, output)).to eq(0)

 NoMethodError:
   undefined method `chomp' for nil:NilClass
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:31:in `get_col_choice'
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:42:in `get_col_choice'
 # ./connect_four_game_spec.rb:57:in `block (3 levels) in <top (required)>'

3) ConnectFourGame#get_col_choice notifies the user if the column they chose is already full of pieces
 Failure/Error: expect(output.string).to include("The column you chose is fully occupied.")
   expected "" to include "The column you chose is fully occupied."
 # ./connect_four_game_spec.rb:62:in `block (3 levels) in <top (required)>'

4) ConnectFourGame#get_col_choice notifies the user their input is invalid when a non-numeric string is entered
 Failure/Error: $connect_four.get_col_choice(input, output)

 NoMethodError:
   undefined method `chomp' for nil:NilClass
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:31:in `get_col_choice'
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:42:in `get_col_choice'
 # ./connect_four_game_spec.rb:67:in `block (3 levels) in <top (required)>'

5) ConnectFourGame#get_col_choice column choice is out of bounds notifies the user their column choice is out of bounds when col is greater than 6
 Failure/Error: $connect_four.get_col_choice(input, output)

 NoMethodError:
   undefined method `chomp' for nil:NilClass
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:31:in `get_col_choice'
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:42:in `get_col_choice'
 # ./connect_four_game_spec.rb:74:in `block (4 levels) in <top (required)>'

6) ConnectFourGame#get_col_choice column choice is out of bounds notifies the user their column choice is out of bounds when col is less than 0
 Failure/Error: $connect_four.get_col_choice(input, output)

 NoMethodError:
   undefined method `chomp' for nil:NilClass
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:31:in `get_col_choice'
 # /home/learnsometing/Desktop/the_Odin_Project/ruby/connect-four/lib/connect_four_game.rb:42:in `get_col_choice'
 # ./connect_four_game_spec.rb:80:in `block (4 levels) in <top (required)>'

Finished in 0.02399 seconds (files took 0.1108 seconds to load)
12 examples, 6 failures

Failed examples:

rspec ./connect_four_game_spec.rb:51 # ConnectFourGame#get_col_choice notifies users which player gets to choose a column
rspec ./connect_four_game_spec.rb:56 # ConnectFourGame#get_col_choice returns the player's column choice
rspec ./connect_four_game_spec.rb:60 # ConnectFourGame#get_col_choice notifies the user if the column they chose is already full of pieces
rspec ./connect_four_game_spec.rb:66 # ConnectFourGame#get_col_choice notifies the user their input is invalid when a non-numeric string is entered
rspec ./connect_four_game_spec.rb:73 # ConnectFourGame#get_col_choice column choice is out of bounds notifies the user their column choice is out of bounds when col is greater than 6
rspec ./connect_four_game_spec.rb:79 # ConnectFourGame#get_col_choice column choice is out of bounds notifies the user their column choice is out of bounds when col is less than 0

以下是我为get_col_choice编写的测试

describe '#get_col_choice' do
    let(:output) { StringIO.new }
    let(:input) { StringIO.new("0\n") }
    it 'notifies users which player gets to choose a column' do
        $connect_four.get_col_choice(input, output)
        expect(output.string).to include("Player 2, choose a column from 0-6: ")
    end

    it "returns the player's column choice" do
        expect($connect_four.get_col_choice(input, output)).to eq(0)
    end

    it 'notifies the user if the column they chose is already full of pieces' do
        6.times { $connect_four.board.add_game_piece_to(0, "\u2468") }
        expect(output.string).to include("The column you chose is fully occupied.")
    end

    let(:input) { StringIO.new("!\n") }        
    it 'notifies the user their input is invalid when a non-numeric string is entered' do
        $connect_four.get_col_choice(input, output)
        expect(output.string).to include("Your choice of column is invalid. Try again.")
    end

    context 'column choice is out of bounds' do
        let(:input) { StringIO.new("7\n") }
        it 'notifies the user their column choice is out of bounds when col is greater than 6' do
            $connect_four.get_col_choice(input, output)
            expect(output.string).to include("The column you chose is out of bounds.")
        end

        let(:input) { StringIO.new("-1\n") }
        it 'notifies the user their column choice is out of bounds when col is less than 0' do
            $connect_four.get_col_choice(input, output)
            expect(output.string).to include("The column number you chose is out of bounds.")
        end
    end        
end

Answer 1

我能够通过从get_col_choice中删除input和output来解决问题

def get_col_choice
    print "Player #{@player}, choose a column from 0-6: " 
    input_string = gets.chomp
    begin
        col_choice = Integer(input_string)
        raise("The column you chose is out of bounds.") if out_of_bounds?(col_choice)
        raise("The column you chose is fully occupied.") if @board.unavailable?(col_choice)
        return col_choice
    rescue TypeError, ArgumentError
        puts "Your choice of column is invalid. Try again."            
    rescue RuntimeError => err
        puts err.message
    end
    get_col_choice
end

在我的rspec文件中，我没有使用StringIO将我预期的行为注入到get_col_choice中，而是使用存根gets来返回触发预期行为所需的值：

#code left out for brevity
before(:each) do
    @game = ConnectFourGame.new
end

describe '#get_col_choice' do
    before(:each) do
        allow($stdout).to receive(:write)
        @game.player = 1
    end

    context 'valid input' do
        before(:each) do
            allow(@game).to receive(:gets) {"0\n"}
        end

        it 'notifies users which player gets to choose a column' do
            expect{ @game.get_col_choice }.to output('Player 1, choose a column from 0-6: ').to_stdout
        end

        it "returns the user's column choice as an integer" do
            expect(@game.get_col_choice).to eq(0)
        end
    end

    context 'invalid input' do
        output_expectation = Proc.new{ expect { @game.get_col_choice }.to output(output).to_stdout }

        it 'notifies the user if the column they chose is already full of pieces' do
            allow(@game).to receive(:gets).and_return("0\n", "1\n")
            6.times { @game.board.add_game_piece_to(0, "\u2648") }
            output = "Player 1, choose a column from 0-6: The column you chose is fully occupied.\nPlayer 1, choose a column from 0-6: "
            output_expectation
        end

        it 'notifies the user their input is invalid when a non-numeric string is entered' do
            allow(@game).to receive(:gets).and_return("foo\n", "0\n")
            output = "Player 1, choose a column from 0-6: Your choice of column is invalid. Try again.\nPlayer 1, choose a column from 0-6: "
            output_expectation
        end

        it 'notifies the user their column choice is out of bounds when col is greater than 6' do
            allow(@game).to receive(:gets).and_return("7\n", "0\n")
            output = "Player 1, choose a column from 0-6: The column you chose is out of bounds.\nPlayer 1, choose a column from 0-6: "
            output_expectation
        end

        it 'notifies the user their column choice is out of bounds when col is less than 0' do
            allow(@game).to receive(:gets).and_return("-1\n", "0\n")
            output = "Player 1, choose a column from 0-6: The column you chose is out of bounds.\nPlayer 1, choose a column from 0-6: "
            output_expectation
        end
    end        
end

我在以前的get_col_choice实现中收到错误的原因是，在StringIO收到我的第一个输入字符串后，它关闭了，从而产生了一个nil值，我试图在该值上调用gets。