update file structure [ci skip]

tools/files/files_test.go

@@ -0,0 +1,11 @@
+package files
+
+import "testing"
+
+func TestCopyFile(t *testing.T) {
+	err := CopyFile("test_data/file_to_copy.txt", "test_data/copied_file.txt")
+
+	if err != nil {
+		t.Error("Can't copy the file.")
+	}
+}