function addError(context, line, error) {
    context.find('.test-title').append('<pre></pre>');
    var message = _jQuery.trim(line() + '\n\n' + formatException(error));
    context.find('.test-title pre:last').text(message);
  }
Add an error to a step.

@param {Object} The JQuery wrapped context
@param {function()} fn() that should return the file/line number of the error
@param {Object} the error.