用void方法来测试场景

void testMeWell() throws SomeException {..}

不抛出异常:

Junit5

assertDoesNotThrow(() -> {
    testMeWell();
});

Java 8让这变得容易多了，Kotlin/Scala更是如此。

我们可以写一个小工具类

class MyAssertions{
  public static void assertDoesNotThrow(FailingRunnable action){
    try{
      action.run()
    }
    catch(Exception ex){
      throw new Error("expected action not to throw, but it did!", ex)
    }
  }
}

@FunctionalInterface interface FailingRunnable { void run() throws Exception }

然后你的代码就变得很简单:

@Test
public void foo(){
  MyAssertions.assertDoesNotThrow(() -> {
    //execute code that you expect not to throw Exceptions.
  }
}

如果你不能使用java -8，我会使用一种非常古老的java工具:任意的代码块和一个简单的注释

//setup
Component component = new Component();

//act
configure(component);

//assert 
/*assert does not throw*/{
  component.doSomething();
}

最后，用kotlin，一种我最近爱上的语言:

fun (() -> Any?).shouldNotThrow() 
    = try { invoke() } catch (ex : Exception){ throw Error("expected not to throw!", ex) }

@Test fun `when foo happens should not throw`(){

  //...

  { /*code that shouldn't throw*/ }.shouldNotThrow()
}

尽管有很多空间可以随意改变你想要如何表达这一点，但我一直喜欢流畅的断言。

关于

你想错了。只需测试您的功能:如果抛出异常，测试将自动失败。如果没有抛出异常，您的测试将全部显示为绿色。

这在原则上是正确的，但在结论上是不正确的。

Java允许控制流的异常。这是由JRE运行时本身在Double等api中完成的。parseDouble通过NumberFormatException和路径。通过invalidpatheexception获取。

Given you've written a component that validates Number strings for Double.ParseDouble, maybe using a Regex, maybe a hand-written parser, or perhaps something that embeds some other domain rules that restricts the range of a double to something specific, how best to test this component? I think an obvious test would be to assert that, when the resulting string is parsed, no exception is thrown. I would write that test using either the above assertDoesNotThrow or /*comment*/{code} block. Something like

@Test public void given_validator_accepts_string_result_should_be_interpretable_by_doubleParseDouble(){
  //setup
  String input = "12.34E+26" //a string double with domain significance

  //act
  boolean isValid = component.validate(input)

  //assert -- using the library 'assertJ', my personal favourite 
  assertThat(isValid).describedAs(input + " was considered valid by component").isTrue();
  assertDoesNotThrow(() -> Double.parseDouble(input));
}

我还鼓励您使用Theories或Parameterized对输入参数化这个测试，这样您就可以更容易地对其他输入重复使用这个测试。或者，如果您想要与众不同，您可以使用测试生成工具(以及这个工具)。TestNG对参数化测试有更好的支持。

What I find particularly disagreeable is the recommendation of using @Test(expectedException=IllegalArgumentException.class), this exception is dangerously broad. If your code changes such that the component under test's constructor has if(constructorArgument <= 0) throw IllegalArgumentException(), and your test was supplying 0 for that argument because it was convenient --and this is very common, because good generating test data is a surprisingly hard problem--, then your test will be green-bar even though it tests nothing. Such a test is worse than useless.

AssertJ可以处理这种情况:

assertThatNoException().isThrownBy(() -> System.out.println("OK"));

查看文档了解更多信息https://assertj.github.io/doc/#assertj-core-exception-assertions-no-exception

如果您不幸捕获了代码中的所有错误。 你可以愚蠢地做

class DumpTest {
    Exception ex;
    @Test
    public void testWhatEver() {
        try {
            thisShouldThrowError();
        } catch (Exception e) {
            ex = e;
        }
        assertEquals(null,ex);
    }
}

JUnit5为此添加了assertAll()方法。

assertAll( () -> foo() )

来源:JUnit 5 API

JUnit 5 (Jupiter)提供了三个函数来检查异常是否存在:

● 断言全部（）

断言所有提供的可执行文件 不要抛出异常。

● assertDoesNotThrow（）

类的执行 提供可执行/供应商 不抛出任何类型的异常。

此函数可用 JUnit 5.2.0以来(2018年4月29日)。

●assertThrows ()

断言所提供的可执行文件的执行 抛出expectedType的异常 并返回异常。

例子

package test.mycompany.myapp.mymodule;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.Test;

class MyClassTest {

    @Test
    void when_string_has_been_constructed_then_myFunction_does_not_throw() {
        String myString = "this string has been constructed";
        assertAll(() -> MyClass.myFunction(myString));
    }
    
    @Test
    void when_string_has_been_constructed_then_myFunction_does_not_throw__junit_v520() {
        String myString = "this string has been constructed";
        assertDoesNotThrow(() -> MyClass.myFunction(myString));
    }

    @Test
    void when_string_is_null_then_myFunction_throws_IllegalArgumentException() {
        String myString = null;
        assertThrows(
            IllegalArgumentException.class,
            () -> MyClass.myFunction(myString));
    }

}