你如何在 Dart 中对异常进行单元测试?

问题描述

考虑一个基于传递的参数执行一些异常处理的函数:

Consider a function that does some exception handling based on the arguments passed:

List range(start, stop) {
    if (start >= stop) {
      throw new ArgumentError("start must be less than stop");
    }
    // remainder of function
}

如何测试是否引发了正确类型的异常?

How do I test that the right kind of exception is raised?

推荐答案

在这种情况下，有多种方法可以测试异常.简单地测试是否引发了非特定异常:

In this case, there are various ways to test the exception. To simply test that an unspecific exception is raised:

expect(() => range(5, 5), throwsException);

测试是否引发了正确类型的异常:

to test that the right type of exception is raised:

有几个用于一般目的的预定义匹配器，例如 throwsArgumentError、throwsRangeError、throwsUnsupportedError 等.对于不存在预定义匹配器的类型，您可以使用 TypeMatcher.

there are several predefined matchers for general purposes like throwsArgumentError, throwsRangeError, throwsUnsupportedError, etc.. for types for which no predefined matcher exists, you can use TypeMatcher<T>.

expect(() => range(5, 2), throwsA(TypeMatcher<IndexError>()));

确保不会引发异常:

expect(() => range(5, 10), returnsNormally);

测试异常类型和异常信息:

to test the exception type and exception message:

expect(() => range(5, 3),
    throwsA(predicate((e) => e is ArgumentError && e.message == 'start must be less than stop')));

这是另一种方法:

expect(() => range(5, 3),
  throwsA(allOf(isArgumentError, predicate((e) => e.message == 'start must be less than stop'))));

(感谢 Google 的 Graham Wheeler 提供的最后两个解决方案).

(Thanks to Graham Wheeler at Google for the last 2 solutions).

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