Added JsonVariant::clear()

test/ElementProxy/clear.cpp

@@ -0,0 +1,28 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+using namespace ARDUINOJSON_NAMESPACE;
+
+TEST_CASE("ElementProxy::clear()") {
+  DynamicJsonDocument doc(4096);
+  doc.addElement();
+  ElementProxy<JsonDocument&> ep = doc[0];
+
+  SECTION("size goes back to zero") {
+    ep.add(42);
+    ep.clear();
+
+    REQUIRE(ep.size() == 0);
+  }
+
+  SECTION("isNull() return true") {
+    ep.add("hello");
+    ep.clear();
+
+    REQUIRE(ep.isNull() == true);
+  }
+}