Added string conversions for equality-comparable classes

Provides a Catch::toString() overload for the following SFML classes, that support at least operator== and operator!=, and can thus be used in Catch assertion expressions:
* String
* Time
* Vector2<T>
* Vector3<T>
* VideoMode
* Color
* Rect<T>

The intermediate header UnitTests.hpp is introduced to ensure string conversion visibility.
Do not include <catch.hpp> directly any longer.

test/CMakeLists.txt

@@ -2,6 +2,7 @@ set(SRCROOT "${PROJECT_SOURCE_DIR}/test/src")
 
 SET(SRC
     "${SRCROOT}/Main.cpp"
+    "${SRCROOT}/UnitTests.cpp"
     "${SRCROOT}/Vector2.cpp"
     "${SRCROOT}/Rect.cpp"
 )

test/src/Rect.cpp

@@ -1,6 +1,6 @@
 #include <SFML/Graphics/Rect.hpp>
 #include <SFML/System/Vector2.hpp>
-#include <catch.hpp>
+#include "UnitTests.hpp"
 
 TEST_CASE("sf::Rect class")
 {

test/src/UnitTests.cpp

@@ -0,0 +1,42 @@
+// Note: No need to increase compile time by including UnitTests.hpp
+#include <SFML/System/String.hpp>
+#include <SFML/System/Time.hpp>
+#include <SFML/Window/VideoMode.hpp>
+#include <SFML/Graphics/Color.hpp>
+#include <sstream>
+
+
+// String conversions for Catch framework
+namespace Catch
+{
+    std::string toString(const sf::String& string)
+    {
+        return string.toAnsiString();
+    }
+
+    std::string toString(sf::Time time)
+    {
+        std::ostringstream stream;
+        stream << time.asMicroseconds() << "us";
+        return stream.str();
+    }
+
+    std::string toString(const sf::VideoMode& videoMode)
+    {
+        std::ostringstream stream;
+        stream << videoMode.width << "x" << videoMode.height << "x" << videoMode.bitsPerPixel;
+        return stream.str();
+    }
+
+    std::string toString(const sf::Color& color)
+    {
+        std::ostringstream stream;
+        stream << "0x" << std::hex << color.toInteger() << std::dec
+               << " (r=" << static_cast<int>(color.r)
+               << ", g=" << static_cast<int>(color.g)
+               << ", b=" << static_cast<int>(color.b)
+               << ", a=" << static_cast<int>(color.a) << ")";
+
+        return stream.str();
+    }
+}

test/src/UnitTests.hpp

@@ -0,0 +1,58 @@
+// Header for SFML unit tests.
+//
+// For a new test case, include this header and not <catch.hpp> directly.
+// This ensures that string conversions are visible and can be used by Catch for debug output.
+
+#ifndef SFML_UNITTESTS_HPP
+#define SFML_UNITTESTS_HPP
+
+#include <SFML/System/Vector2.hpp>
+#include <SFML/System/Vector3.hpp>
+#include <SFML/Graphics/Rect.hpp>
+#include <sstream>
+#include <catch.hpp>
+
+
+// Forward declarations for non-template types
+namespace sf
+{
+    class Color;
+    class String;
+    class Time;
+    class VideoMode;
+}
+
+// String conversions for Catch framework
+namespace Catch
+{
+    std::string toString(const sf::String& string);
+    std::string toString(sf::Time time);
+    std::string toString(const sf::VideoMode& videoMode);
+    std::string toString(const sf::Color& color);
+
+    template <typename T>
+    std::string toString(const sf::Vector2<T>& vector)
+    {
+        std::ostringstream stream;
+        stream << "(" << vector.x << ", " << vector.y << ")";
+        return stream.str();
+    }
+
+    template <typename T>
+    std::string toString(const sf::Vector3<T>& vector)
+    {
+        std::ostringstream stream;
+        stream << "(" << vector.x << ", " << vector.y << ", " << vector.z << ")";
+        return stream.str();
+    }
+
+    template <typename T>
+    std::string toString(const sf::Rect<T>& rect)
+    {
+        std::ostringstream stream;
+        stream << "(left=" << rect.left << ", top=" << rect.top << ", width=" << rect.width << ", height=" << rect.height << ")";
+        return stream.str();
+    }
+}
+
+#endif // SFML_UNITTESTS_HPP

test/src/Vector2.cpp

@@ -1,5 +1,5 @@
 #include <SFML/System/Vector2.hpp>
-#include <catch.hpp>
+#include "UnitTests.hpp"
 
 // Use sf::Vector2i for tests. Test coverage is given, as there are no template specializations.