It is important that a brewer regularly check the fermentability of the wort produced. A very simple and effective method is a forced fermentation test. This test can be performed by any brewer with or without a lab. The forced fermentation test consists of aseptically pulling a wort sample (post heat-exchanger) into a sterile sample container and inoculating with a very high yeast cell count (Dried yeast works fine). Agitate the container often. Check the gravity after 36-48 hours to determine terminal gravity. This test will give you a good idea of where your fermentation should finish. If your main fermentation does not reach the same level as your forced ferment, you know you have a problem in the fermenter (pitch rate, temperature, oxygenation). If both your main fermentation and the forced ferment finish out of spec (too high or too low), you know that you have a problem on the brewing side (mash temperature, times, crush, ingredients).