Added a variant unittest

unittest/CMakeLists.txt

@@ -30,3 +30,4 @@ make_test (test_interval "interval.cpp")
 make_test (test_hierarchy "hierarchy.cpp")
 make_test (test_tagged_pointer "tagged_pointer.cpp")
 make_test (test_type_list "type_list_tests.cpp")
+make_test (test_variant "variant.cpp")

unittest/variant.cpp

@@ -0,0 +1,69 @@
+#include <ecs/ecs.h>
+#define CATCH_CONFIG_MAIN
+#include "catch.hpp"
+
+// Create a variant tree
+//   A
+//  / \
+// B   C
+// |
+// D
+//
+struct A {};
+struct B { using variant_of = A; };
+struct C { using variant_of = A; };
+struct D { using variant_of = B; };
+
+TEST_CASE("Variant components", "[component][variant]") {
+	ecs::runtime rt;
+
+	// First, add 'A'
+	rt.add_component(0, A{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 1);
+	REQUIRE(rt.get_component_count<B>() == 0);
+	REQUIRE(rt.get_component_count<C>() == 0);
+	REQUIRE(rt.get_component_count<D>() == 0);
+
+	// Add 'B' and 'C'. Both are variants of 'A', so 'A' will be removed
+	rt.add_component(0, B{}, C{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 0);
+	REQUIRE(rt.get_component_count<B>() == 1);
+	REQUIRE(rt.get_component_count<C>() == 1);
+	REQUIRE(rt.get_component_count<D>() == 0);
+
+	// Add 'D', which is only a variant of 'B' and 'A', so 'B' will be removed.
+	// 'C' remains untouched
+	rt.add_component(0, D{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 0);
+	REQUIRE(rt.get_component_count<B>() == 0);
+	REQUIRE(rt.get_component_count<C>() == 1);
+	REQUIRE(rt.get_component_count<D>() == 1);
+
+	// Add 'A', which a parent variant to all other components,
+	// so they will all be removed
+	rt.add_component(0, A{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 1);
+	REQUIRE(rt.get_component_count<B>() == 0);
+	REQUIRE(rt.get_component_count<C>() == 0);
+	REQUIRE(rt.get_component_count<D>() == 0);
+
+	// Add 'D', which is a variant of 'A'.
+	rt.add_component(0, D{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 0);
+	REQUIRE(rt.get_component_count<B>() == 0);
+	REQUIRE(rt.get_component_count<C>() == 0);
+	REQUIRE(rt.get_component_count<D>() == 1);
+
+	// Add 'A' again
+	rt.add_component(0, A{});
+	rt.commit_changes();
+	REQUIRE(rt.get_component_count<A>() == 1);
+	REQUIRE(rt.get_component_count<B>() == 0);
+	REQUIRE(rt.get_component_count<C>() == 0);
+	REQUIRE(rt.get_component_count<D>() == 0);
+}