How to work around the fact that std::function has no operator==?

Problem: The following code would be very expressive and concise, if not necessarily fast, were it not for the fact that it does not compile.

It does not compile because you cannot compare std::function instances with operator==(). And std::find() tries to do exactly that.

Of course, I could go for an entirely different kind of implementation, but stubborn as I am and fond as I am with the code below, I am looking for something "closest as possible" which works.

Who can provide me a pretty rewrite of the code below which does the same thing?

#include <functional>
#include <vector>

typedef std::function<bool(int)> Tester_t;
typedef std::vector<Tester_t> TesterSet_t;

bool Test(TesterSet_t &candidates, int foo)
{
    TesterSet_t dropouts;
    for( auto& tester : candidates )
    {
        if(!tester(foo))    
        {
            droputs.push_back(tester);
        }
    }

    while(!dropouts.empty())
    {
        // The following line is not compiling because std::function has no operator==()
        TesterSet_t::iterator culprit = 
            std::find( candidates.begin(), candidates.end(), dropouts.back() );
        candidates.erase(culprit);
        dropouts.pop_back();
    }
    return !candidates.empty();
}