tests: introduce catch2 unit tests infrastructure.

Catch2 is a multi-paradigm test framework for C++.
It is primarily distributed as a single header file,
very easy and simple to adopt this to thorvg project.

This patch introduces catch2 infrastsructure and one prototype as a sample.

You can refer "testInitializer.cpp", how to add unit test!
while ignoring else files such as "catch2.hpp", "testMain.cpp"

Also, enable Unit-tests with meson option when you change any thorvg code.

$meson build -Dtests=true.

launch tvgUnitTest in the build result then verify 100% coverage
before submitting any patches.

meson.build

@@ -47,16 +47,24 @@ headers = [include_directories('inc'), include_directories('.')]
 subdir('inc')
 subdir('src')
 
+if get_option('tests') == true
+   subdir('test')
+endif
+
 summary = '''
 
 Summary:
-    thorvg version :        @0@
-    Build type      :       @1@
+    ThorVG version  :       @0@
+    Build Type      :       @1@
     Prefix          :       @2@
+    Tests           :       @3@
+    Examples        :       @4@
 '''.format(
         meson.project_version(),
         get_option('buildtype'),
         get_option('prefix'),
+        get_option('tests'),
+        get_option('examples'),
     )
 
 message(summary)

meson_options.txt

@@ -33,6 +33,11 @@ option('examples',
     value: false,
     description: 'Enable building examples')
 
+option('tests',
+   type: 'boolean',
+   value: false,
+   description: 'Enable building Unit Tests')
+
 option('log',
     type: 'boolean',
     value: false,

test/meson.build

@@ -0,0 +1,11 @@
+test_file = [
+    'testMain.cpp',
+    'testInitializer.cpp',
+]
+
+tests = executable('tvgUnitTests',
+    test_file,
+    include_directories : headers,
+    link_with : thorvg_lib)
+
+test('Unit Tests', tests)

test/testInitializer.cpp

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2020-2021 Samsung Electronics Co., Ltd. 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;
+
+
+TEST_CASE("Basic initialization", "[tvgInitializer]")
+{
+    REQUIRE(Initializer::init(CanvasEngine::Sw, 0) == Result::Success);
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::Success);
+}
+
+TEST_CASE("Multiple initialization", "[tvgInitializer]")
+{
+    REQUIRE(Initializer::init(CanvasEngine::Sw, 0) == Result::Success);
+    REQUIRE(Initializer::init(CanvasEngine::Sw, 0) == Result::Success);
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::Success);
+
+    REQUIRE(Initializer::init(CanvasEngine::Sw, 0) == Result::Success);
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::Success);
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::Success);
+}
+
+TEST_CASE("Negative termination", "[tvgInitializer]")
+{
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::InsufficientCondition);
+}
+
+TEST_CASE("Many threads", "[tvgInitializer]")
+{
+    REQUIRE(Initializer::init(CanvasEngine::Sw, -1) == Result::FailedAllocation);
+    REQUIRE(Initializer::term(CanvasEngine::Sw) == Result::InsufficientCondition);
+}
+
+TEST_CASE("Invalid engine", "[tvgInitializer]")
+{
+    REQUIRE(Initializer::init(CanvasEngine(0), 0) == Result::InvalidArguments);
+}

test/testMain.cpp

@@ -0,0 +1,5 @@
+// The only purpose of this file is to DEFINE the catch config so it can include main()
+
+#define CATCH_CONFIG_MAIN // This tells Catch to provide a main() - only do this in one cpp file
+
+#include "catch.hpp"