al_test.o: In function `test_wave()':
al_test.cpp:(.text+0x1a7): undefined reference to `min::wave::wave(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
...

all: libmgl.a libmgl.so

libmgl.so: $(OBJECTS)
    $(LD) $* $(LDFLAGS) -shared -o $@

libmgl.a: $(OBJECTS)
    $(AR) $(ARFLAGS) libmgl.a $^

%.o: %.cpp
    $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(INCLUDES) -c -o $@ $<

#include <iostream>
#include "twave.h"
int main()
{
    try
    {
        bool out = true;
        out = out && test_wave();
        // out = out && test_ogg();
        // out = out && test_sound_buffer();
        if (out)
        {
            std::cout << "Sound tests passed!" << std::endl;
            return 0;
        }
    }
    catch (std::exception &ex)
    {
        std::cout << ex.what() << std::endl;
    }

    std::cout << "Sound tests failed!" << std::endl;
    return -1;
}

#include <stdexcept>
#include "min/wave.h"
bool test_wave()
{
    bool out = true;

    // Load invention wav file
    {
        const min::wave sound = min::wave("data/sound/invention_no_1.wav");

        // File should not be mono
        out = out && !sound.is_mono();
        if (!out)
        {
            throw std::runtime_error("Failed wave file not is_mono");
        }

        // Other checks that aren't important...
    }

    return out;
}

#ifndef __WAVE__
#define __WAVE__
#include <string>
namespace min {
class wave
{
  private:
    void load(const std::string);
  public:
    wave(const std::string&);
};
}
#endif

#include "wave.h"

min::wave::wave(const std::string &file)
{
    load(file);
}

// Definition of `load` omitted; I don't think it's important,
// but know that it is here

g++ -c -Imin/ al_test.cpp -o al_test.o
g++ al_test.o -L. -lmgl -lX11 -lGL -lfreetype -lopenal -lvorbisfile -o bin/al_test

$(CXX) $* $(LDFLAGS) -shared -o $@

g++ -L. -lmgl -lX11 -lGL -lfreetype -lopenal -lvorbisfile -o bin/al_test al_test.o

g++ -c -Imin/ al_test.cpp -o al_test.o