+ fix unused variables warning

+ added tests

Primitive doesn't work well in algorithms. Also, almost (?) all
algorithms are working with integer values on nodes/edges, so this
should be just fine.

Also simplify lambdas in tests to capture everything

Also simplify lambdas in tests to capture everything

Helps to track failures

It now stores number of edges, instead of just bool indicating
that there is an edge

Also edited to use ASSERT_EQUAL for better fail messages

testCopyConstruct test now passes

Also modified add/remove node/edge methods so they now return bool
indicating success

Also modified add/remove node/edge methods so they now return bool
indicating success

Without a IUndirectedGraph implementation yet

dynamic cast would only provide better backtrace (with nullptr),
but wouldn't prevent the crash

also fix build