More fixes for contrib test to use external JSON library.

Author: kotl

contrib/test/FirebaseArduino_test.cpp

@@ -16,6 +16,7 @@
 
 #include "FirebaseObject.h"
 #include "gtest/gtest.h"
+#include "WString.h"
 
 TEST(FirebaseObjectTest, GetBool) {
   FirebaseObject obj("true");

contrib/test/modem/Makefile

@@ -34,6 +34,7 @@ FIREBASE_ROOT = ../../..
 PROJECT_ROOT = ../..
 SRC_ROOT = $(PROJECT_ROOT)/src
 FIREBASE_SRC_ROOT = $(FIREBASE_ROOT)/src
+ARDUINOJSON_DIR=$(ARDUINO_HOME)/libraries/ArduinoJson
 
 # Flags passed to the preprocessor.
 # Set Google Test and Google Mock's header directories as system
@@ -45,6 +46,7 @@ CPPFLAGS += -isystem $(GTEST_DIR)/include -isystem $(GMOCK_DIR)/include \
 		-I$(PROJECT_ROOT)/test/dummies \
 		-I$(PROJECT_ROOT)/src \
 		-I$(FIREBASE_ROOT)/src \
+        -I$(ARDUINOJSON_DIR)/src \
 		-I$(PROJECT_ROOT)
 
 # Flags passed to the C++ compiler.