test accessor: added accessor test unit test.

@Issue: https://github.com/Samsung/thorvg/issues/1243

test/meson.build

@@ -1,4 +1,5 @@
 test_file = [
+    'testAccessor.cpp',
     'testFill.cpp',
     'testInitializer.cpp',
     'testMain.cpp',

test/testAccessor.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2022 ThorVG Project. All rights reserved.
+
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <thorvg.h>
+#include "catch.hpp"
+
+using namespace tvg;
+#include <stdio.h>
+
+TEST_CASE("Accessor Creation", "[tvgAccessor]")
+{
+    auto accessor = tvg::Accessor::gen();
+    REQUIRE(accessor);
+
+    auto accessor2 = tvg::Accessor::gen();
+    REQUIRE(accessor2);
+}
+
+
+TEST_CASE("Set", "[tvgAccessor]")
+{
+    REQUIRE(Initializer::init(CanvasEngine::Sw, 0) == Result::Success);
+
+    auto canvas = SwCanvas::gen();
+    REQUIRE(canvas);
+
+    uint32_t buffer[100*100];
+    REQUIRE(canvas->target(buffer, 100, 100, 100, SwCanvas::Colorspace::ABGR8888) == Result::Success);   
+
+    auto picture = Picture::gen();
+    REQUIRE(picture);
+    REQUIRE(picture->load(TEST_DIR"/logo.svg") == Result::Success);
+
+    auto accessor = tvg::Accessor::gen();
+    REQUIRE(accessor);
+
+    //Case 1
+    picture = accessor->set(move(picture), nullptr);
+    REQUIRE(picture);
+
+    //Case 2
+    auto f = [](const tvg::Paint* paint) -> bool
+    {
+        if (paint->identifier() == tvg::Shape::identifier()) {
+            auto shape = (tvg::Shape*) paint;
+            uint8_t r, g, b, a;
+            shape->fillColor(&r, &g, &b, &a);
+            if (r == 37 && g == 47 && b == 53)
+                shape->fill(0, 0, 255, a);
+        }
+        return true;
+    };
+
+    picture = accessor->set(move(picture), f);
+    REQUIRE(picture);
+
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::Success);
+}