Added JsonArrayConst, JsonObjectConst, and JsonVariantConst

test/JsonVariant/subscript.cpp

@@ -120,3 +120,55 @@ TEST_CASE("JsonVariant::operator[]") {
   }
 #endif
 }
+
+TEST_CASE("JsonVariantConst::operator[]") {
+  DynamicJsonDocument doc;
+  JsonVariant var = doc.to<JsonVariant>();
+  JsonVariantConst cvar = var;
+
+  SECTION("The JsonVariant is undefined") {
+    REQUIRE(0 == cvar.size());
+    REQUIRE(cvar["0"].isNull());
+    REQUIRE(cvar[0].isNull());
+  }
+
+  SECTION("The JsonVariant is a string") {
+    var.set("hello world");
+    REQUIRE(0 == cvar.size());
+    REQUIRE(cvar["0"].isNull());
+    REQUIRE(cvar[0].isNull());
+  }
+
+  SECTION("The JsonVariant is a JsonArray") {
+    JsonArray array = var.to<JsonArray>();
+
+    SECTION("get value") {
+      array.add("element at index 0");
+      array.add("element at index 1");
+
+      REQUIRE(2 == cvar.size());
+      REQUIRE(std::string("element at index 0") == cvar[0]);
+      REQUIRE(std::string("element at index 1") == cvar[1]);
+      REQUIRE(std::string("element at index 0") ==
+              var[static_cast<unsigned char>(0)]);  // issue #381
+      REQUIRE(cvar[666].isNull());
+      REQUIRE(cvar[3].isNull());
+      REQUIRE(cvar["0"].isNull());
+    }
+  }
+
+  SECTION("The JsonVariant is a JsonObject") {
+    JsonObject object = var.to<JsonObject>();
+
+    SECTION("get value") {
+      object["a"] = "element at key \"a\"";
+      object["b"] = "element at key \"b\"";
+
+      REQUIRE(2 == cvar.size());
+      REQUIRE(std::string("element at key \"a\"") == cvar["a"]);
+      REQUIRE(std::string("element at key \"b\"") == cvar["b"]);
+      REQUIRE(cvar["c"].isNull());
+      REQUIRE(cvar[0].isNull());
+    }
+  }
+}