class_idea.hh

#include <concepts>

enum class ButtonError {
	None,
	StuckDown,
	NoisyPress,
	NoisyRelease,
	MultipleHighs,
	Unknown,
};

template<typename T>
concept BoardC = requires(T t, unsigned chan) {
	{
		t.read_button(chan)
	} -> std::same_as<bool>;
	t.set_indicator(chan, bool{});
	t.set_error_indicator(chan, ButtonError{});
};

template<BoardC Board>
class ButtonTester {
	Board board;
	unsigned cur_chan = 0;

public:
	bool check() {
		board.read_button(cur_chan);
		cur_chan++;
		return true;
	}
};

////// in project:

struct SWNButtonIO {
	bool read_button(unsigned num) { return false; }
	void set_indicator(unsigned num, bool high) {}
	void set_error_indicator(unsigned num, ButtonError err) {}
};

void test_buttons() {
	ButtonTester<SWNButtonIO> checker;

	while (!checker.check()) {
	}
}