Improve build system and add support for tests

Makefile

@@ -1,10 +1,35 @@
 include Makeconf
 
-$(info $(modules))
-objs := $(addsuffix .o,$(modules))
+emu-objs := $(addsuffix .o,$(modules))
+test-targets := $(patsubst %,tests/%.bin, $(tests))
+
+clean-objs := $(emu-objs) $(test-targets) libemu.a vgbc
+
+.PHONY: all test clean
+
+all: vgbc $(test-targets)
+
+clean:
+	rm -rf $(clean-objs)
+
+test: $(test-targets)
+	@for test in $(tests); do \
+		if ./tests/$$test.bin; then \
+			echo "-- $$test successful"; \
+		else \
+			echo "-- $$test failed"; \
+			exit 1; \
+		fi \
+	done
 
 %.o: %.cpp
 	g++ $(CXX_FLAGS) -c -o $@ $^
 
-vgbc: $(objs)
-	g++ -o $@ $^
+libemu.a: $(emu-objs)
+	ar -rc $@ $^
+
+tests/%.bin: tests/%.cpp libemu.a
+	g++ $(CXX_FLAGS) -o $@ $^
+
+vgbc: main.c libemu.a
+	g++ $(CXX_FLAGS) -o $@ $^