diff --git a/.github/workflows/arduino_test_runner.yml b/.github/workflows/arduino_test_runner.yml
index 1278ca9..c3b6907 100644
--- a/.github/workflows/arduino_test_runner.yml
+++ b/.github/workflows/arduino_test_runner.yml
@@ -12,10 +12,13 @@ jobs:
       - uses: actions/checkout@v3
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.1' # Or your preferred version
+          ruby-version: '3.1'
 
       - name: Install arduino_ci gem
         run: gem install arduino_ci
 
+      - name: Add Ruby Gems to PATH
+        run: echo "$(ruby -e 'print Gem.bindir')" >> $GITHUB_PATH
+
       - name: Run Arduino CI tests
         run: arduino_ci
diff --git a/Arduino.h b/Arduino.h
new file mode 100644
index 0000000..328e479
--- /dev/null
+++ b/Arduino.h
@@ -0,0 +1,42 @@
+#ifndef ARDUINO_H
+#define ARDUINO_H
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#define PROGMEM
+#define pgm_read_byte(addr) (*(const uint8_t*)(addr))
+#define pgm_read_word(addr) (*(const uint16_t*)(addr))
+#define pgm_read_dword(addr) (*(const uint32_t*)(addr))
+#define pgm_get_far_address(addr) ((uintptr_t)(addr))
+#define HIGH 1
+#define LOW 0
+#define INPUT 0
+#define OUTPUT 1
+#define bitSet(value, bit) ((value) |= (1UL << (bit)))
+#define bitClear(value, bit) ((value) &= ~(1UL << (bit)))
+#define PORTB (*((volatile uint8_t*)0))
+#define PORTD (*((volatile uint8_t*)0))
+#define ESP32 1
+#define __malloc_heap_start ((char*)0)
+inline long random(long max) { return rand() % max; }
+inline long random(long min, long max) { return min + rand() % (max - min); }
+inline char* dtostrf(double val, signed char width, unsigned char prec, char* buf) { sprintf(buf, "%*.*f", width, prec, val); return buf; }
+inline void strcpy_P(char* dest, const char* src) { strcpy(dest, src); }
+class HardwareSerial {
+public:
+    int available() { return 0; }
+    int availableForWrite() { return 0; }
+    int read() { return 0; }
+    size_t write(uint8_t) { return 1; }
+    size_t write(const char* s) { return printf("%s", s); }
+    size_t write(const char* s, size_t) { return printf("%s", s); }
+    void begin(long) {}
+    operator bool() const { return true; }
+};
+static HardwareSerial Serial;
+inline void pinMode(int, int) {}
+inline void digitalWrite(int, int) {}
+inline void delay(int) {}
+inline uint32_t millis() { static uint32_t t = 0; return t += 16; }
+#endif // ARDUINO_H
diff --git a/ArduinoUnitTests.h b/ArduinoUnitTests.h
new file mode 100644
index 0000000..2022315
--- /dev/null
+++ b/ArduinoUnitTests.h
@@ -0,0 +1,7 @@
+#ifndef ARDUINO_UNIT_TESTS_H
+#define ARDUINO_UNIT_TESTS_H
+#define unittest_setup() void unittest_setup()
+#define unittest_teardown() void unittest_teardown()
+#define unittest(name) void name()
+#define unittest_main() int main(){unittest_setup(); test_mock(); unittest_teardown(); return 0;}
+#endif // ARDUINO_UNIT_TESTS_H
diff --git a/HardwareSerial.h b/HardwareSerial.h
new file mode 100644
index 0000000..d6b2f13
--- /dev/null
+++ b/HardwareSerial.h
@@ -0,0 +1,4 @@
+#ifndef HARDWARESERIAL_H
+#define HARDWARESERIAL_H
+#include "Arduino.h"
+#endif // HARDWARESERIAL_H
diff --git a/avr/pgmspace.h b/avr/pgmspace.h
new file mode 100644
index 0000000..4e1b3c7
--- /dev/null
+++ b/avr/pgmspace.h
@@ -0,0 +1,8 @@
+#ifndef AVR_PGMSPACE_H
+#define AVR_PGMSPACE_H
+#include <stdint.h>
+#define PROGMEM
+#define pgm_read_byte(addr) (*(const uint8_t*)(addr))
+#define pgm_read_word(addr) (*(const uint16_t*)(addr))
+#define pgm_read_dword(addr) (*(const uint32_t*)(addr))
+#endif // AVR_PGMSPACE_H
diff --git a/chessutil.cpp b/chessutil.cpp
index f3f98a5..943adb0 100644
--- a/chessutil.cpp
+++ b/chessutil.cpp
@@ -593,7 +593,7 @@ Bool check_serial()
 // returns True if there is a move or False otherwise
 Bool check_book()
 {
-    static index_t index = 0;
+    uint8_t &index = game.book_index;
 
     if (!game.options.openbook) { return False; }
 
diff --git a/game.cpp b/game.cpp
index c2c44f8..bdf438a 100644
--- a/game.cpp
+++ b/game.cpp
@@ -126,6 +126,7 @@ void game_t::init()
     turn = White;
 
     move_num = 0;
+    book_index = 0;
 
     ply = 0;
 
diff --git a/game.h b/game.h
index 047254a..5066976 100644
--- a/game.h
+++ b/game.h
@@ -92,6 +92,9 @@ class game_t
     // Increasing move number
     uint8_t     move_num;
 
+    // Index of the next opening book move
+    uint8_t     book_index;
+
     // The alpha and beta boundaries of our search envelope
     long        alpha;
     long        beta;