1. A quantum-logic test-development system comprising a processor, a memory coupled to the processor, and a computer-readable hardware storage device coupled to the processor, the storage device containing program code configured to be run by the processor via the memory to implement a method for using direct sums and invariance groups to test partially symmetric quantum-logic circuits, the method comprising: the system receiving architectural information about a quantum-logic circuit that has at least four inputs and at least one output; the system, as a function of the architectural information, dividing the at least four inputs into two or more non-intersecting subsets; the system creating a set of groups that each comprise a subset, selected from the set of two or more non-intersecting subsets, and one or more permutation operations, where no individual operation of the one or more permutation operations comprises any characteristic capable of precluding the individual operation from-being performed upon inputs comprised by the selected subset; the system generating a direct sum of the set of groups, where the direct sum identifies an invariance group of a function that represents functionality of the quantum-logic circuit, where the invariance group comprises a set of invariant permutations, where each permutation of the set of invariant permutations identifies a permutation of two or more inputs comprised by one and only one subset of the two or more non-intersecting subsets, and where no output of the quantum-logic circuit changes state when any permutation of the set of invariant permutations is performed upon the at least four inputs of the quantum-logic circuit; the system optimizing a procedure for testing the quantum-logic circuit, where the procedure comprises a series of tests that each verify correct operation of the quantum-logic circuit in response to receiving a distinct input vector of a set of input vectors, and where the optimizing comprises deleting from the series of tests any test associated with an input vector, where the input vector comprises no characteristic capable of precluding the input vector from being generated by performing a permutation of the set of invariant permutations upon a distinct input vector associated with a previous test of the series of tests.