java - JUnitを使用したユニットテスト中に例外を処理するにはどうすればよいですか？

Question

メソッドが例外をスローする場合、そのメソッドが実際に予期された例外をスローしていることを確認するためのテストケースを作成するにはどうすればよいですか？

Answer 1

In newest versions of JUnit it works that way:

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExpectedException;

public class NumberFormatterExceptionsTests {

    @Rule
    public ExpectedException thrown = ExpectedException.none();

    @Test
    public void shouldThrowExceptionWhenDecimalDigitsNumberIsBelowZero() {
        thrown.expect(IllegalArgumentException.class); // you declare specific exception here
        NumberFormatter.formatDoubleUsingStringBuilder(6.9, -1);
    }
}

more on ExpectedExceptions:

http://kentbeck.github.com/junit/javadoc/4.10/org/junit/rules/ExpectedException.html

http://alexruiz.developerblogs.com/?p=1530

// These tests all pass.
 public static class HasExpectedException {
        @Rule
        public ExpectedException thrown= ExpectedException.none();

        @Test
        public void throwsNothing() {
    // no exception expected, none thrown: passes.
        }

        @Test
        public void throwsNullPointerException() {
                thrown.expect(NullPointerException.class);
                throw new NullPointerException();
        }

        @Test
        public void throwsNullPointerExceptionWithMessage() {
                thrown.expect(NullPointerException.class);
                thrown.expectMessage("happened?");
                thrown.expectMessage(startsWith("What"));
                throw new NullPointerException("What happened?");
        }
 }

Answer 2

Two options that I know of.

If using junit4

@Test(expected = Exception.class)

or if using junit3

try {
    methodThatThrows();
    fail("this method should throw excpetion Exception");
catch (Exception expect){}

Both of these catch Exception. I would recommend catching the exception you are looking for rather than a generic one.

Answer 3

目的の例外をキャッチして、次のようなことを行うことができますassertTrue(true)。

@Test
testIfThrowsException(){
    try{
        funcThatShouldThrowException(arg1, agr2, agr3);
        assertTrue("Exception wasn't thrown", false);
    }
    catch(DesiredException de){
        assertTrue(true);
    }
}