You never define bodies for TestBed's execute and setAlgorithm functions.
Instead, you are defining two global functions with the same name.
You forgot to give those functions the proper scope:
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/*SelectionAlgorithm * algorithm; // <- these probably should not be global
AlgorithmSortAll * all; // they probably should be members of TestBed
AlgorithmSortK * toKey;*/
//..
void TestBed::setAlgorithm(int type, int k) { // <- note the 'TestBed::'
//..
void TestBed::execute() // <- note the 'TestBed::'
