The biggest cause of test failure is lack of preparation and practice. Lots and lots of people fail every year and we know and sympathise with how they must feel.
However, from some of the million failures, there is a small number who do not complete the test at all, but have the test stopped by the examiner.

If an examiner decides it is not safe to continue, they can bring the test to an end. This is done for their safety, your safety and the safety of other road users.

They are frequently checked themselves by a senior examiner so they will always try to give you the benefit of the doubt. However, sometimes the examiner will feel they are not safe, so they terminate the test. They will do this by stopping you in a safe place and telling you that the test is being terminated and that you have failed the test. They will explain why they have done this and will hand you the fail sheet. (Your instructor will help to interpret the points and advise you on correcting them).

When the examiner has terminated the test, they have to get back to the test centre. They can not drive the learner car back themselves due to insurance reasons. So you will be given two options.
You can wait in the car until the examiner has walked back to the test centre where he will give directions to your instructor to where you are, or,
You can lock the car up and walk back to the test centre with the examiner to meet your instructor.

Did you have enough lessons? Your Instructor will use the faults relating to your failure to improve your performance before you take another test.