优化了平衡，尤其对于向后倾倒的几种极限情况进行优化

Shibo-main-TOMMY/lib/ArduinoJson/extras/tests/JsonVariant/nullptr.cpp

@@ -0,0 +1,43 @@
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("nullptr") {
+  DynamicJsonDocument doc(4096);
+  JsonVariant variant = doc.to<JsonVariant>();
+
+  SECTION("JsonVariant == nullptr") {
+    REQUIRE(variant == nullptr);
+    REQUIRE_FALSE(variant != nullptr);
+  }
+
+  SECTION("JsonVariant != nullptr") {
+    variant.set(42);
+
+    REQUIRE_FALSE(variant == nullptr);
+    REQUIRE(variant != nullptr);
+  }
+
+  SECTION("JsonVariant.set(nullptr)") {
+    variant.set(42);
+    variant.set(nullptr);
+
+    REQUIRE(variant.isNull());
+  }
+
+  SECTION("JsonVariant.set(nullptr) with unbound reference") {
+    JsonVariant unboundReference;
+
+    unboundReference.set(nullptr);
+
+    REQUIRE(variant.isNull());
+  }
+
+  SECTION("JsonVariant.is<nullptr_t>()") {
+    variant.set(42);
+    REQUIRE(variant.is<std::nullptr_t>() == false);
+
+    variant.clear();
+    REQUIRE(variant.is<std::nullptr_t>() == true);
+  }
+}