There are several reasons why you should take the testing serious and do them with maximum effort when your box has testing week(s). Most of the reasons, are similar to why you would test in school or at your job, but there are also a few others that are specific to sport.
Benchmarking is used by both athletes and coaches to track progress. You, as an athlete should be keeping a log or a record book of your workouts (especially lifting and benchmark WODs). When you test, you can look back in your records to see the progress you have made since the last testing. You may have improved on time, or increased weight. You may have went Rx this time where you scaled the last time you tested. Most of you know if you are improving in the box, but this puts an actual value on how much you are improving.
The coaches use benchmarking to see in what areas the members are improving the most/least. If the average mile run time went down considerably but the average snatch max stayed the same, the coaches (programmer) can make adjustments in order to balance things out.
Finding your strengths and weaknesses
This goes hand and hand with benchmarking. If you are not tracking your results, it is very difficult to know exactly where you are strong and/or weak. In a typical box, you will test every 3-4 months in various movement and benchmark WODs. You may find that in you initial testing when you started CrossFit, you were not very good at pull ups but you very strong in your CrossFit Total. The next time around you were decent at pull ups, still strong at CrossFit Total but your Olympic lifts were not as high as you would like. Strengths and weaknesses will always be changing for as long as you CrossFit. Even though the top CrossFit athletes are good at many aspects of CrossFit, they all still have weaknesses.
After testing is complete, and you are done recording your results, you can use the numbers to set goals for yourself. Your goals can be to increase weight, have a faster time, or to complete WODs at Rx instead of scaled. Whatever the goals are that you set, make sure they are specific. Don't just say you want to 'increase squat weight'. How much do you want to increase is by? Don't say, 'reduce Fran time.' How fast do you want to do it?
By setting specific numbers for your goals, it creates an extra motivation for yourself. If you say, 'increase weight', then you don't really have to work much harder to get a five pound personal record. However, if you say increase my squat from 275 to 300 then you have a specific goal and you know you need to work hard and push yourself to get the goal.
Weights for Lifting and WODs
In many lifting programs in the box, it is important to know what weight to use. Your program may use percentages for each set or they may say, 'work to heavy sets'. Either way, if you don't know what your max, then how will you know what percentage to use or how to go heavy without going too heavy?
Knowing your numbers will also help you choose weights for some WODs. If your max deadlift is 235, and the WOD Rx weight is 255, you may want to consider dropping the weight in order to complete the WOD successfully. The opposite may also occur though. You may think you are not very good at front squat so you usually scale the weight for all WODs with front squats. However, when you tested, your one rep max weight was 50 pounds above most Rx WOD weight.
Pushing yourself to another level
Lastly, when you show up to test, it can bring your intensity to another level. In a way, it is almost acts like a competition. You may be competing with other friends, others in your class or on the board, but mostly it is competing against yourself. If you know your previous numbers, you are competing to beat that number. Because of the environment this creates, your adrenaline will pump through those veins, you will push yourself to another level. This intensity is well above the intensity you bring to most daily WODs.
There are several reasons why you should participate in your boxes Testing Week (s). Don't cherry pick those benchmarks you are not good at or you don't want to complete. That typically means that is a weakness and you should be working on those weaknesses. Choose why you ARE going to give it your best effort. Show up to class, focus on the WOD, do the best you possibly can, record those results, then set new goals! This will help you become stronger, faster and fit.