implement basic unit testing

Makefile

@@ -5,6 +5,7 @@
 IDIR = ./include
 BDIR = ./build
 SDIR = ./src
+TDIR = ./tests
 
 include config.mk
 
@@ -34,6 +35,9 @@ lib: $(SDIR)/libglacier.c
 	$(CC) $(SDIR)/libglacier.c -c $(LIBFLAGS) -o $(BDIR)/lib/libglacier.o
 	$(AR) -rc $(BDIR)/lib/libglacier.a build/lib/libglacier.o
 
+test: $(BDIR) $(TDIR)/Makefile
+	make -f tests/Makefile
+
 install_lib: $(BDIR)/lib/libglacier.a
 	@echo "[INFO]"
 	@echo "[INFO] Installing library to PREFIX/lib..."
@@ -59,3 +63,6 @@ install: install_lib install_head
 
 clean:
 	rm -rf $(BDIR)
+
+distclean: $(BDIR) $(TDIR)/test-suite
+	rm -rf $(BDIR) $(TDIR)/test-suite