Don’t rely on exception messages

Since the dotless 1.1 release we are finally able to present you with good error messages, telling you what line/column the problem was encountered etc. This has led to some tests like this one:

public void DivisionByZero()
{
    AssertExpressionError("Attempted to divide by zero.", 5, "20px / 0");
    AssertExpressionError("Attempted to divide by zero.", 14, "1 + 2 - 3 * 4 / 0");
    AssertExpressionError("Attempted to divide by zero.", 6, "1 + 2 / 0 - 3 * 4 / 0");
}

Usually you just check the exception type, but in this case it’s a generic ParseException that has the additional line/column  info on it and does not wrap the DivideByZeroException in it’s InnerException. Obviously the above failed on my machine due to my German locale and I was getting a different exception message.

I first tried to set the thread’s culture to en-GB but this only changes how formats are handled, there are no English exception texts installed on a German Windows machine.

The obvious solution then was to not hard-code the exception message but retrieve it from the DivideByZeroException:

[Test]
public void DivisionByZero()
{
    var divideByZeroException = new DivideByZeroException();
    AssertExpressionError(divideByZeroException.Message, 5, "20px / 0");
    AssertExpressionError(divideByZeroException.Message, 14, "1 + 2 - 3 * 4 / 0");
    AssertExpressionError(divideByZeroException.Message, 6, "1 + 2 / 0 - 3 * 4 / 0");
}

Takeaway: Make sure you tests run on all locales if your tests rely on exception messages.