Added memoryUsage() to JsonArray, JsonObject, and JsonVariant

test/JsonArray/memoryUsage.cpp

@@ -0,0 +1,42 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("JsonArray::memoryUsage()") {
+  DynamicJsonDocument doc(4096);
+  JsonArray arr = doc.to<JsonArray>();
+
+  SECTION("return 0 if uninitialized") {
+    JsonArray unitialized;
+    REQUIRE(unitialized.memoryUsage() == 0);
+  }
+
+  SECTION("JSON_ARRAY_SIZE(0) if empty") {
+    REQUIRE(arr.memoryUsage() == JSON_ARRAY_SIZE(0));
+  }
+
+  SECTION("JSON_ARRAY_SIZE(1) after add") {
+    arr.add("hello");
+    REQUIRE(arr.memoryUsage() == JSON_ARRAY_SIZE(1));
+  }
+
+  SECTION("includes the size of the string") {
+    arr.add(std::string("hello"));
+    REQUIRE(arr.memoryUsage() == JSON_ARRAY_SIZE(1) + 6);
+  }
+
+  SECTION("includes the size of the nested array") {
+    JsonArray nested = arr.createNestedArray();
+    nested.add(42);
+    REQUIRE(arr.memoryUsage() == 2 * JSON_ARRAY_SIZE(1));
+  }
+
+  SECTION("includes the size of the nested arrect") {
+    JsonObject nested = arr.createNestedObject();
+    nested["hello"] = "world";
+    REQUIRE(arr.memoryUsage() == JSON_OBJECT_SIZE(1) + JSON_ARRAY_SIZE(1));
+  }
+}