public static T assertThrows()

in src/main/java/org/junit/Assert.java [998:1029]

• 28 lines of code
• 4 McCabe index (conditional complexity)

    public static <T extends Throwable> T assertThrows(String message, Class<T> expectedThrowable,
            ThrowingRunnable runnable) {
        try {
            runnable.run();
        } catch (Throwable actualThrown) {
            if (expectedThrowable.isInstance(actualThrown)) {
                @SuppressWarnings("unchecked") T retVal = (T) actualThrown;
                return retVal;
            } else {
                String expected = formatClass(expectedThrowable);
                Class<? extends Throwable> actualThrowable = actualThrown.getClass();
                String actual = formatClass(actualThrowable);
                if (expected.equals(actual)) {
                    // There must be multiple class loaders. Add the identity hash code so the message
                    // doesn't say "expected: java.lang.String<my.package.MyException> ..."
                    expected += "@" + Integer.toHexString(System.identityHashCode(expectedThrowable));
                    actual += "@" + Integer.toHexString(System.identityHashCode(actualThrowable));
                }
                String mismatchMessage = buildPrefix(message)
                        + format("unexpected exception type thrown;", expected, actual);

                // The AssertionError(String, Throwable) ctor is only available on JDK7.
                AssertionError assertionError = new AssertionError(mismatchMessage);
                assertionError.initCause(actualThrown);
                throw assertionError;
            }
        }
        String notThrownMessage = buildPrefix(message) + String
                .format("expected %s to be thrown, but nothing was thrown",
                        formatClass(expectedThrowable));
        throw new AssertionError(notThrownMessage);
    }