Expected Exceptions Message fails to match multi-line messages

Providing an expectedExceptionsMessageRegExp value to a test should intuitively match any provided regex. However since Invoker.messageRegExpMatches() uses Pattern.matches() instead of Matcher.find() or Pattern.compile(re, Pattern.DOTALL) it is possible for a message to match or fail arbitrarily based on the existence of a newline.

Even if the user should be expected to explicitly drop the pattern into dotall mode, the current error message is unclear and confusing:

The exception was thrown with the wrong message: expected ".*Illegal.*" but got "Illegal State.
Two lines breaks the test."

Example test:

import org.testng.annotations.Test;

public class MessagePatternTest {
    @Test(expectedExceptions=IllegalStateException.class, expectedExceptionsMessageRegExp=".*Illegal.*")
    public void singleLine() {
        throw new IllegalStateException("Illegal State.");
    }

    @Test(expectedExceptions=IllegalStateException.class, expectedExceptionsMessageRegExp=".*Illegal.*")
    public void multiLine() {
        throw new IllegalStateException("Illegal State.\nTwo lines breaks the test.");
    }

    @Test(expectedExceptions=IllegalStateException.class, expectedExceptionsMessageRegExp="(?s).*Illegal.*")
    public void multiLineDOTALL() {
        throw new IllegalStateException("Illegal State.\nTwo lines breaks the test.");
    }
}

[nthexwn]

Had a similar problem, found this on Google, solved my own problem, and came back to help. 😃

You’ve got the right idea with the (?s) modifier on . in your multiLineDOTALL test before “Illegal”. However, the linebreak in the exception you’re throwing occurs AFTER “Illegal”, so you need another (?s).* there as well:

expectedExceptionsMessageRegExp="(?s).*Illegal(?s).*"

EDIT: This is incorrect. See dimo414’s post below.

[yusong-shen]

In case someone stucks at older version before fix but still want this to work (should rarely be the case at 2020 😂 ), here is a workaround : replace all the . to (\\S|\\s) in expectedExceptionsMessageRegExp

Edited : I misread the comment, adding (?s) at the beginning of regex is way more cleaner.