Question

我在Espresso中进行了一项测试，需要断言某个操作会导致抛出异常。

然而，似乎Espresso框架吞噬了原始异常并且只显示PerformException。

Answer 1

最终我找到了办法。我创建了一个自定义的Hamcrest匹配器，允许您验证嵌套异常。

public class NestedExceptionMatcher extends TypeSafeMatcher<Throwable> {

    private final Class<?> mExpectedType;
    private final Matcher<String> mMessageMatcher;

    static NestedExceptionMatcher expectNestedThrowable(Class<?> expectedType, Matcher<String> messageMatcher) {
        return new NestedExceptionMatcher(expectedType, messageMatcher);
    }

    NestedExceptionMatcher(Class<?> expectedType, Matcher<String> messageMatcher) {
        mExpectedType = expectedType;
        mMessageMatcher = messageMatcher;
    }

    @Override
    protected boolean matchesSafely(Throwable item) {
        boolean matches = isMatch(item);

        Throwable currentThrowable = item.getCause();
        while (!matches && currentThrowable != null) {
            matches = isMatch(currentThrowable);
            currentThrowable = currentThrowable.getCause();
        }

        return matches;
    }

    @Override
    public void describeTo(Description description) {
        description
                .appendText("expects type ")
                .appendValue(mExpectedType)
                .appendText(" with a message ")
                .appendDescriptionOf(mMessageMatcher);
    }

    private boolean isMatch(Throwable t) {
        return t.getClass().isAssignableFrom(mExpectedType) && mMessageMatcher.matches(t.getMessage());
    }
}

然后你可以在测试中使用它如下：

public class SomeActivityTest {

    @Rule
    public ActivityTestRule<SomeActivity> mRule = new ActivityTestRule<>(
            SomeActivity.class, false, false);

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

    @Test
    public void testClick_whenInvalidParamsAreSet_shouldThrowException() {
        mRule.launchActivity(getIntentWithInvalidParams());
        mExceptionRule.expect(expectNestedThrowable(
                IllegalArgumentException.class,
                containsString("parameter isn't defined")
        ));

        onView(withId(R.id.my_btn)).perform(click());
    }

    private Intent getIntentWithInvalidParams() {
        ...
    }
}

Answer 2

你可以这样做

@Test( expected = ArrayIndexOutOfBoundsException.class) //OR any other  
throwable
public void myTest() {

}

Answer 3

我使用try / catch块：

try {
    methodThatThrowsException();
    fail("Expected exception not thrown");
} catch (CustomException customException) {
}

Answer 4

为什么不使用这个：

 @Test(expected = PerformException::class)
    fun traderSummaryContainer_notScroll() {
        onView(withId(R.id.traderSummaryContainer))
                .perform(scrollTo())
    }

Answer 5

使用正常的try catch解决了我的问题，我知道嵌套了异常。但是我们仍然可以按原因进行检查：

    var error: Throwable? = null
    try {
        onView(something).perform(click())
    } catch (e: Throwable) {
        error = e;
    }
    assert(error!!.cause is MySpecificException)
    assert(error!!.cause!!.message == "My specific error message")

我尝试了上述自定义的Hamcrest匹配器方法，但是最终我得到了不稳定的测试，因此最终进入了这一测试。

Answer 6

为什么不使用 Assert.assertThrows(Class expectedThrowable, ThrowingRunnable runnable) 或 Assert.assertThrows(String message, Class expectedThrowable, ThrowingRunnable runnable)

在Android Espresso测试中断言异常

6 个答案: