There are no tests for the following rules:

1. 
Default references are used in deactivate operations (see clause 20.5.3) in order to 
identify the default to be deactivated.

Reason: No reason for a dedicated test, tested in 20.5.3.

2. 
Default references have meaning only within the test component instances they are 
activated, i.e. a default reference assigned to a default variable in test component 
instance "a1" of type "A" has no meaning in test component instance "a2" of type "A".

Reason: No meaningful test for the rule. The most common way to use defaults is 
deactivate operation specified in 20.5.3 which contains a dedicated test related
to this requirement.

3.
The actual data representation of the default type shall be resolved externally by the 
test system. This allows abstract test cases to be specified independently of any real 
TTCN-3 runtime environment, in other words TTCN-3 does not restrict the implementation 
of a test system with respect to the handling and identification of defaults.

Reason: This rule is only declaratory and doesn't set any binding requirements which
could be verified.
