Graph tests with expect_exception

GraphTests

void graph_tests(const digraph &g, digraph::nodename source,
                digraph::nodename destination, const set<string> & except_on )
{
    auto throw_return = [] ()
        { cout << "Caught Expected Exception" << endl; };
    auto tst = [exc_return, except_on] (string fcn, auto a)
        {
            bool expect_throw = except_on.end()!=except_on.find(fcn);
            auto normal_return = [fcn] (auto retval)
                { cout << fcn << " visiting " << retval << endl; };
            expect_exception(a, expect_throw, throw_return, normal_return );
        };

    cout << endl << "=====> Beginning a test set" << endl;
    tst("BFS", [g, source] () { return g.bfs(source); } );
    tst("DFS", [g, source] () { return g.dfs(source); } );
    tst("Topsort", [g] () { return g.topsort(); } );
    tst("Dijkstra", [g, source, destination] ()
        { return g.dijkstra(source, destination); } );
    tst("Bellman", [g, source] ()
        { return get<0>(g.bellman_ford(source).get()); } );
};


void main( )
{
    // create the graphs x, y, z

    set<string> none;
    graph_tests(y,'A','D', none); // no algorithms will throw
    graph_tests(z,'A','D', none); // no algorithms will throw
    graph_tests(x,'A','D', set<string>{"Topsort"}); // topsort will throw
}