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问题描述
Scalatest 中有什么东西可以让我通过 println 语句测试标准输出的输出吗?
Is there something in Scalatest that will allow me to test the output to the standard out via a println statement?
到目前为止，我主要使用 FunSuite with ShouldMatchers.
So far I've mainly been using FunSuite with ShouldMatchers.
例如我们如何检查
object Hi {
def hello() {
println("hello world")
}
}
推荐答案
在控制台上测试打印语句的常用方法是稍微不同地构建您的程序，以便您可以拦截这些语句.例如，您可以引入 Output 特征:
The usual way to test print statements on the console is to structure your program a bit differently so that you can intercept those statements. You can for example introduce an Output trait:
trait Output {
def print(s: String) = Console.println(s)
}
class Hi extends Output {
def hello() = print("hello world")
}
并且在您的测试中，您可以定义另一个特征 MockOutput 实际上拦截调用:
And in your tests you can define another trait MockOutput actually intercepting the calls:
trait MockOutput extends Output {
var messages: Seq[String] = Seq()
override def print(s: String) = messages = messages :+ s
}
val hi = new Hi with MockOutput
hi.hello()
hi.messages should contain("hello world")
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