Added JsonVariant::containsKey()

test/JsonVariant/CMakeLists.txt

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

test/JsonVariant/containsKey.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::containsKey()") {
+  DynamicJsonDocument doc(4096);
+  JsonVariant var = doc.to<JsonVariant>();
+
+  SECTION("containsKey(const char*) returns true") {
+    var["hello"] = "world";
+
+    REQUIRE(var.containsKey("hello") == true);
+    REQUIRE(var.containsKey("world") == false);
+  }
+
+  SECTION("containsKey(std::string) returns true") {
+    var["hello"] = "world";
+
+    REQUIRE(var.containsKey(std::string("hello")) == true);
+    REQUIRE(var.containsKey(std::string("world")) == false);
+  }
+}