All our dogs in our breeding program have done the following health tests:
( Obligatory to be a member of the Miniature Bull Terriër Vriendenkring )

# Colour Heart Doppler test to diagnose any abnormality in valves, determine  
    murmurs, aorta stenosis and insufficiency .
# UPC test (urine ) or bloodtest to show the creatinine and ureum levels that give  
    us an insight in how are the kidneys working .
# DNA test to establish the mutation on the gens that can cause PLL 
    (Primary Lens Luxation)  3 different outcomes affected, carrier and clear.

DNA test – What do I do with the results?
The dog is homozygous for the mutation (two copies of the mutation) -
genetically affected: The dog is highly likely to develop lens luxation in its
lifetime. We would recommend that you contact an ophthalmologist close to you
and discuss the situation with him/her. Y
Regular ophthalmic examinations (every 6-12 months) from the age of 18 months should be performed and treatment instigated as appropriate.
The dog is heterozygous for the mutation (one copy of the mutation, one
normal gene) - carrier: Heterozygous dogs have been reported to suffer from
lens luxation. Currently the risk of a heterozygote, or carrier, developing clinical
signs of lens luxation is currently estimated to be between 2 and 20%; however
the true risk is probably closer to 2% than 20% and further studies are underway
to produce an accurate estimate for all breeds. Regular ophthalmic examinations
(every 6-12 months) are recommended from the age of 2 years.
The dog is clear of the mutation (two normal genes): The dog is very unlikely
to develop lens luxation. No ophthalmic examination is needed; however the dog
should be examined by your veterinary surgeon if eye problems occur.
Remember that other ocular diseases can occur and a lens luxation can still be
caused by other ocular problems or trauma.
My dog carries the mutation – what about breeding?
Ocular health is important but only one aspect of a dog’s general health.
Removing all dogs that carry the mutation (homozygous and heterozygous dogs)
from the breeding population may result in a significant reduction in the genetic
diversity of many breeds. This could mean that inbreeding would increase and
allow other genetic diseases to emerge. This is particularly likely to be the case
for numerically small breeds (eg. Miniature Bull terrier, Tibetan terrier) and for
breeds for which the mutation frequency is very high. Therefore, we strongly
advise breeders to consider all their dogs for breeding, regardless of
their PLL genotype. GENETICALLY AFFECTED and CARRIER dogs can
be bred with, but should only be bred to DNA tested, CLEAR dogs. All
puppies from any litter that has at least one CARRIER parent should be
DNA tested, so that the CARRIERS can be identified and followed
clinically throughout their lives.

( article Animal Health Trust UK )
The laboratories where you can do the PLL test are found at the links- page
Laboklin, AHT and OFFA

To check if the dog is hearing both way's.