JsonVariant automatically promotes to JsonObject or JsonArray on write

test/JsonVariant/add.cpp

@@ -0,0 +1,39 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+
+#include <ArduinoJson.h>
+#include <stdint.h>
+#include <catch.hpp>
+
+static const char* null = 0;
+
+TEST_CASE("JsonVariant::add()") {
+  DynamicJsonDocument doc(4096);
+  JsonVariant var = doc.to<JsonVariant>();
+
+  SECTION("No argument") {
+    JsonVariant nested = var.add();
+
+    REQUIRE(var.is<JsonArray>() == true);
+    REQUIRE(nested.isNull() == true);
+  }
+
+  SECTION("integer") {
+    var.add(42);
+
+    REQUIRE(var.as<std::string>() == "[42]");
+  }
+
+  SECTION("const char*") {
+    var.add("hello");
+
+    REQUIRE(var.as<std::string>() == "[\"hello\"]");
+  }
+
+  SECTION("std::string") {
+    var.add(std::string("hello"));
+
+    REQUIRE(var.as<std::string>() == "[\"hello\"]");
+  }
+}