Fix up CI tests

tests/src/lib/Arduino.h

@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
+#include "Print.h"
 
 
 extern "C"{

tests/src/lib/Print.h

@@ -0,0 +1,28 @@
+/*
+ Print.h - Base class that provides print() and println()
+ Copyright (c) 2008 David A. Mellis.  All right reserved.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef Print_h
+#define Print_h
+
+class Print {
+    public:
+        virtual size_t write(uint8_t) = 0;
+};
+
+#endif