Added support for CMake's unity builds

extras/tests/JsonVariant/add.cpp

@@ -6,8 +6,6 @@
 #include <stdint.h>
 #include <catch.hpp>
 
-static const char* null = 0;
-
 TEST_CASE("JsonVariant::add()") {
   DynamicJsonDocument doc(4096);
   JsonVariant var = doc.to<JsonVariant>();

extras/tests/JsonVariant/as.cpp

@@ -10,9 +10,9 @@ namespace my {
 using ARDUINOJSON_NAMESPACE::isinf;
 }  // namespace my
 
-static const char* null = 0;
-
 TEST_CASE("JsonVariant::as()") {
+  static const char* null = 0;
+
   DynamicJsonDocument doc(4096);
   JsonVariant variant = doc.to<JsonVariant>();
 

extras/tests/JsonVariant/clear.cpp

@@ -6,8 +6,6 @@
 #include <stdint.h>
 #include <catch.hpp>
 
-static const char* null = 0;
-
 TEST_CASE("JsonVariant::clear()") {
   DynamicJsonDocument doc(4096);
   JsonVariant var = doc.to<JsonVariant>();

extras/tests/JsonVariant/compare.cpp

@@ -5,8 +5,6 @@
 #include <ArduinoJson.h>
 #include <catch.hpp>
 
-static const char* null = 0;
-
 template <typename T>
 void checkEquals(T a, T b) {
   DynamicJsonDocument doc(4096);
@@ -70,6 +68,8 @@ void checkComparisons(T low, T mid, T high) {
 }
 
 TEST_CASE("JsonVariant comparisons") {
+  static const char* null = 0;
+
   SECTION("Double") {
     checkComparisons<double>(123.44, 123.45, 123.46);
   }

extras/tests/JsonVariant/createNested.cpp

@@ -6,8 +6,6 @@
 #include <stdint.h>
 #include <catch.hpp>
 
-static const char* null = 0;
-
 TEST_CASE("JsonVariant::createNestedObject()") {
   DynamicJsonDocument doc(4096);
   JsonVariant variant = doc.to<JsonVariant>();