Function testOperationValidation

tests/unit/operations.cpp:827–1142

template <NumQubitsFlag Ctrls, NumQubitsFlag Targs, ArgsFlag Args, ApplyFlag Apply>
void testOperationValidation(auto operation) {

    // use any cached Qureg (though postMultiply*() functions accept only density matrices)
    Qureg qureg = getCachedDensmatrs().begin()->second;

    // in lieu of preparing random inputs like testOperationCorrectness()
    // above, we instead obtain simple, fixed, compatible inputs
    auto [ctrls,states,targs] = getFixedCtrlsStatesTargs<Ctrls,Targs,Args>(qureg.numQubits);
    auto furtherArgs = getFixedRemainingArgs<Targs,Args>(targs);

    // calling apiFunc() will pass the above args with their call-time values
    auto apiFunc = [&]() {
        constexpr NumQubitsFlag RevTargs = (Args==paulistr||Args==pauligad)? zero : Targs;
        auto func = [](auto&&... allArgs) { return invokeApiOperation<Ctrls,RevTargs>(allArgs...); };
        std::apply(func, std::tuple_cat(tuple{operation, qureg, ctrls, states, targs}, furtherArgs));
    };

    // convenience vars
    int numQubits = qureg.numQubits;
    int numTargs = (int) targs.size();
    int numCtrls = (int) ctrls.size();

    /// @todo
    /// below, we return from intendedly skipped SECTIONS which
    /// appears to work (does not corrupt test statistics, and
    /// does not attribute skipped tests to having passed the
    /// section) but is an undocumented Catch2 trick. Check safe!

    SECTION( "qureg uninitialised" ) {

        // spoof uninitialised value
        qureg.numQubits = -123;
        REQUIRE_THROWS_WITH( apiFunc(), ContainsSubstring("invalid Qureg") );
    }

    SECTION( "invalid target" ) {

        // not applicable (PauliStr already made from targs)
        if (Args == paulistr || Args == pauligad)
            return;

        // sabotage a target
        int ind = GENERATE_COPY( range(0,numTargs) );
        int val = GENERATE_COPY( -1, numQubits );
        targs[ind] = val;

        REQUIRE_THROWS_WITH( apiFunc(), ContainsSubstring("Invalid target qubit") );
    }

    SECTION( "invalid non-Identity Pauli index" ) {

        if (Args != paulistr && Args != pauligad)
            return;

        PauliStr badStr = getPauliStr("X", {numQubits + 1});
        if constexpr (Args == paulistr) furtherArgs = tuple{ badStr };
        if constexpr (Args == pauligad) furtherArgs = tuple{ badStr, 1 };