Added tests for Flash strings (closes #1070)

test/MixedConfiguration/enable_progmem_1.cpp

@@ -0,0 +1,53 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#include "progmem_emulation.hpp"
+
+#define ARDUINOJSON_ENABLE_PROGMEM 1
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("Flash strings") {
+  DynamicJsonDocument doc(2048);
+
+  SECTION("deserializeJson()") {
+    DeserializationError err = deserializeJson(doc, F("{'hello':'world'}"));
+
+    REQUIRE(err == DeserializationError::Ok);
+    REQUIRE(doc["hello"] == "world");
+  }
+
+  SECTION("JsonDocument::operator[]") {
+    doc[F("hello")] = F("world");
+
+    REQUIRE(doc["hello"] == "world");
+  }
+
+  SECTION("JsonDocument::add()") {
+    doc.add(F("world"));
+
+    REQUIRE(doc[0] == "world");
+  }
+
+  SECTION("JsonVariant::set()") {
+    JsonVariant var = doc.to<JsonVariant>();
+
+    var.set(F("world"));
+
+    REQUIRE(var == "world");
+  }
+
+  SECTION("MemberProxy::operator==") {
+    doc["hello"] = "world";
+
+    REQUIRE(doc["hello"] == F("world"));
+  }
+
+  SECTION("ElementProxy::operator==") {
+    doc.add("world");
+
+    REQUIRE(doc[0] == F("world"));
+  }
+}