As has already been intimated, the tests are not meant to be fair. It can seem harsh, god knows I know, as I've been there with the tests this year, but you have to stop looking at this as a barrier to stop you getting the job you desire. The tests are simply not an unfair barrier to getting that coveted position, but a necessary safety protocol to ensure people with the right skills, aptitude and temperament are then allowed to embark on training. Even then, there are those that will not make the grade.
This will come across as hard faced, but I do not mean it that way, but if you fail the tests you are simply not right for the job. It is irrelevant how ideal you think you would be our how easily you could do the job. Truth is, only drivers really know what the job entails and it is not as straight forward as people 'off the street' might think. The tests measure your aptitude, skills and temperament, not your ability to persevere and eventually learn your way through.
I am certain that passengers, insurance companies and anyone else with a vested interest with safety on the railway would be disconcerted, possibly even horrified, if the process for selecting drivers was made 'fair' rather than considered and rigidly measured.
To answer the original question of whether the tests are fair. On a general level yes, anyone can apply, they are all tested to the same standard with the same tests and test conditions etc. and are all subject to the same 2 strike rule. Everyone had the same opportunity to prepare, access to the same information etc. The only variables are an individual's ability or willingness to prepare for the tests etc fully.
So technically are they fair. Well again, yes. What had to be taken into account here is the position and responsibility of the driver. Although there are many other jobs that carry a similar responsibility or such a requirement to abide by numerous and complex regulations, as well as the technical ability to operate such machinery correctly and safely. But the clincher for me is that there aren't many other jobs where 1 individual is burdened with such singular and total responsibility with all that the role also brings. The environment dictates that the driver and his decisions cannot be mitigated in error by anyone else and that these errors can be catastrophic to human life as well as significant financial implications.
So if you were to fail the test once, it is then up to you as an individual when and if you are ready to take it again. Is fair for the companies as putting people through the process costs them a significant amount of time and money. Most importantly it is fair to the industry as a whole, as the people selected are those most likely to complete the training and carry out the job as required, safely.