在 Ruby 中测试 STDIN [英] Testing STDIN in Ruby
问题描述
我目前正在尝试测试一种基本方法，该方法接收来自用户的一些输入(gets)并输出它(puts).经过一番研究，我找到了一种测试标准输出流的好方法，如下所示:
I'm currently trying to test a basic method that receives some input from the user (gets) and outputs it (puts). After a bit of research I found a good way to test the standard output stream which is the below:
def capture_standard_output(&block)
original_stream = $stdout
$stdout = mock = StringIO.new
yield
mock.string.chomp
ensure
$stdout = original_stream
end
我正在测试的方法是下面的方法，输出和输入指的是我在开始时初始化的 ivars 并指向等效的 $stdout &$标准输入:
The method I'm testing is the one below, output and input refer to ivars which I initialize in the beginning and point to the equivalent $stdout & $stdin:
def ask_for_mark
ouput.puts 'What shall I call you today?'
answer = input.gets.chomp.capitalize
answer
end
现在我已经看到了一些 STDIN 的解决方案，但还没有真正理解其中的任何一个，我绝对不想复制 &粘贴.我唯一一个工作"的人是下面的那个，但它并没有真正起作用，因为当我运行 rspec 时它会暂停并等待输入，只需按 Enter，它就会通过:
Now I've seen some solutions for STDIN but haven't really understood any of them and I definitely don't want to copy & paste. The only one I got to "work" is the one below, but it's not really working since when I run rspec it pauses and waits for input and by simply pressing enter, it passes:
it "takes user's name and returns it" do
output = capture_standard_output { game.ask_for_name }
expect(output).to eq "What shall I call you today?"
game.input.stub(:gets) { 'joe' }
expect(game.ask_for_name).to eq 'Joe'
end
什么是测试 STDIN 的好方法?我一天中的大部分时间都在盯着屏幕(不好，我知道)所以非常感谢一个新的视角和一些帮助:-)
What would be a good way to test STDIN? I've been staring at a screen for most of the day (not good, I know) so a fresh perspective and some help would be greatly appreciated :-)
对于面临类似问题的任何人，我都采用了不同(更简单)的方法.首先，我会在他们自己的方法中分离IO操作.
For anyone facing similar issues, I followed different (simpler) approaches. First, I would separate the IO operations in their own methods.
在输入的情况下，在测试中它可以预先填充所需的数据，所以当 gets 消息被发送时，它将返回由换行符分隔的数据 <代码>\n 像这样:
In the case of input, in the tests it can be pre-populated with the desired data so when the gets message is send, it will return that data which are separated by the newline character \n like so:
input = StringIO.new("one\ntwo\n")
=> #<StringIO:0x007f88152f3510>
input.gets
=> "one\n"
input.gets
=> "two\n"
input.gets
=> nil
这有助于保持被测方法的内部结构的私有性，而无需将测试与实现细节耦合.
This helps with keep the internals of the method under test, private without coupling the tests to the implementation details.
另一种方法是简单地使用多态并传入符合相同api的Fake或Spy对象，而不是调用stdin或stdout，它返回固定数据，或者在 Spy 的情况下，它注册调用.
Another approach is to simply use polymorphism and pass in a Fake or a Spy object that conforms to the same api but instead of making a call to stdin or stdout, it returns canned data instead or in the case of the Spy, it registers the call.
class SpyIO
def initialize
was_called? = false
end
...
def ask_for_name
# call to stdout would normally take place
was_called? = true
end
...
end
class FakeIO
def initialize(data = [some, data])
@data = data
end
def get_user_input
# call to stdin would normally happen
@data.shift
end
...
end
每种方法都有权衡，但我想我会把它们放在这里，以防有人遇到类似问题或考虑选择.
There's tradeoffs in each approach but I thought I'd put these here in case anyone was having similar issues or considering options.
推荐答案
您可以简单地存根 STDIN:
it "takes user's name and returns it" do
output = capture_standard_output { game.ask_for_name }
expect(output).to eq "What shall I call you today?"
allow(STDIN).to receive(:gets) { 'joe' }
expect(game.ask_for_name).to eq 'Joe'
end
实际上，你可以用 STDOUT 做同样的事情，而无需改变 $stdout:
Actually, you can do the same with STDOUT, without needing to change $stdout:
it "takes user's name and returns it" do
expect(STDOUT).to receive(:puts).with("What shall I call you today?")
allow(STDIN).to receive(:gets) { 'joe' }
expect(game.ask_for_name).to eq 'Joe'
end
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