Avoid Arduino.h when all its features are disabled (fixes #1692)

extras/tests/Helpers/Arduino.h

@@ -7,3 +7,5 @@
 #include "api/Print.h"
 #include "api/Stream.h"
 #include "api/String.h"
+
+#define ARDUINO_H_INCLUDED 1

extras/tests/Misc/CMakeLists.txt

@@ -8,6 +8,7 @@ add_executable(MiscTests
 	deprecated.cpp
 	FloatParts.cpp
 	JsonString.cpp
+	NoArduinoHeader.cpp
 	printable.cpp
 	Readers.cpp
 	StringAdapters.cpp

extras/tests/Misc/NoArduinoHeader.cpp

@@ -0,0 +1,20 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright Benoit Blanchon 2014-2021
+// MIT License
+
+#define ARDUINO 1
+#define ARDUINOJSON_ENABLE_PROGMEM 0
+#define ARDUINOJSON_ENABLE_ARDUINO_STRING 0
+#define ARDUINOJSON_ENABLE_ARDUINO_STREAM 0
+#define ARDUINOJSON_ENABLE_ARDUINO_PRINT 0
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("Arduino.h") {
+#ifdef ARDUINO_H_INCLUDED
+  FAIL("Arduino.h should not be included");
+#else
+  INFO("Arduino.h not included");
+#endif
+}