Added unit testing

tests/Makefile

@@ -0,0 +1,22 @@
+AS=riscv32-elf-as
+LD=riscv32-elf-ld
+BUILD_DIR=../build/tests/
+
+S_FILES := $(shell find ./ -name '*.s')
+NAMES = $(basename $(S_FILES))
+OBJECTS=$(patsubst %, $(BUILD_DIR)/%, $(NAMES))
+
+all: $(OBJECTS) run
+
+$(BUILD_DIR):
+	mkdir -p $(BUILD_DIR)
+
+$(BUILD_DIR)/%.o: %.s | $(BUILD_DIR)
+	$(AS) $^ -o $@
+
+$(BUILD_DIR)/%: $(BUILD_DIR)/%.o | $(BUILD_DIR)
+	$(LD) $^ -o $@ -nostdlib
+
+.SILENT: run
+run:
+	bash test.sh