@ 
\subsection{Testing the function module}

Following our standard order, we'll setup for tests at the beginning
and define tests throughout the implementation of functions.
<<function>>=
<<Tests for functions>>
<<Create a test suite for functions>>
@ 
<<Create a test suite for functions>>=
(add-test
        (make-test-suite
                "Functions Test Suite"
                NIL
                <<Functions test suite items>>
        )
        max-test-suite
)
@ 
This test verifies that the type of functions is a type.
<<Tests for functions>>=
(defmethod type-of-functions ((nf nullfix))
    (unless (addr-value-equal 
                (typeaddr-instance *types*) 
                (addr-type *functions*) 
                (addr-value *types*))
            (failure "Type of *functions* is not *types*")
))
@ 
<<Functions test suite items>>=
                ("Type of *functions*" 'nullfix :test-thunk 'type-of-functions)
@ 
We have 4 tests to ensure the domain is ``types'' and the codomain is ``functions''
for both the domain and codomain functions.
<<Tests for functions>>=
(defmethod domain-domain ((nf nullfix))
        (unless (addr-equal (function-apply *domain* *domain*) *functions*)
                (failure "Domain of the domain function is not *functions*")
))

(defmethod domain-codomain ((nf nullfix))
        (unless (addr-equal (function-apply *domain* *codomain*) *functions*)
                (failure "Domain of the codomain function is not *functions*")
))

(defmethod codomain-domain ((nf nullfix))
        (unless (addr-equal (function-apply *codomain* *domain*) *types*)
                (failure "Codomain of the domain function is not *types*")
))

(defmethod codomain-codomain ((nf nullfix))
        (unless (addr-equal (function-apply *codomain* *codomain*) *types*)
                (failure "Codomain of the codomain function is not *types*")
))
@ 
<<Functions test suite items>>=
                ("Domain of domain function" 'nullfix :test-thunk 'domain-domain)
                ("Domain of codomain function" 'nullfix :test-thunk 'domain-codomain)
                ("Codomain of domain function" 'nullfix :test-thunk 'codomain-domain)
                ("Codomain of codomain function" 'nullfix :test-thunk 'codomain-codomain)