Added JsonVariant::clear()

test/JsonVariant/CMakeLists.txt

@@ -5,6 +5,7 @@
 add_executable(JsonVariantTests
 	add.cpp
 	as.cpp
+	clear.cpp
 	compare.cpp
 	copy.cpp
 	createNested.cpp

test/JsonVariant/clear.cpp

@@ -0,0 +1,28 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#include <ArduinoJson.h>
+#include <stdint.h>
+#include <catch.hpp>
+
+static const char* null = 0;
+
+TEST_CASE("JsonVariant::clear()") {
+  DynamicJsonDocument doc(4096);
+  JsonVariant var = doc.to<JsonVariant>();
+
+  SECTION("size goes back to zero") {
+    var.add(42);
+    var.clear();
+
+    REQUIRE(var.size() == 0);
+  }
+
+  SECTION("isNull() return true") {
+    var.add("hello");
+    var.clear();
+
+    REQUIRE(var.isNull() == true);
+  }
+}