What I'm saying to you is this:-
1. UKBA has a list of approved tests and associated approved providers.
2. There is no such thing as a test called A1. That is just the designation of the level of qualification required for spouse visa.
3. Not all of the UKBA approved tests are evaluated at level A1 - Some have a higher level and may be too demanding for some students.
4. Each test has it's own evaluation scoring. The UKBA approved list clearly indicates the level at which they accept for each test ( for example, IELTS test has a minimum level B1 which equates to a score of 4. UKBA will not accept any score less than 4 even if the actual score of the student was equal to A1 level such as 3.5)
5. Your wife needs to select a test which she feels comfortable with and also a testing centre that she can get to easily.
6. Many people on this forum and beyond have elected to take the test called IELTS. The minimum score is 4 which is a level of B1. Despite this being higher than the A1 required they have felt comfortable to take this with their skill level as they felt this was also more convenient with a convenient test centre.
The B1 level of IELTS is certainly not enough for nurses etc.