diff --git a/Source/UnitTests/Core/MMIOTest.cpp b/Source/UnitTests/Core/MMIOTest.cpp
index 97cabda658..c7e183f458 100644
--- a/Source/UnitTests/Core/MMIOTest.cpp
+++ b/Source/UnitTests/Core/MMIOTest.cpp
@@ -22,3 +22,56 @@ TEST(UniqueID, UniqueEnough)
 		ids.insert(unique_id);
 	}
 }
+
+class MappingTest : public testing::Test
+{
+protected:
+	virtual void SetUp()
+	{
+		m_mapping = new MMIO::Mapping();
+	}
+
+	virtual void TearDown()
+	{
+		delete m_mapping;
+	}
+
+	MMIO::Mapping* m_mapping;
+};
+
+TEST_F(MappingTest, ReadConstant)
+{
+	m_mapping->Register(0xCC001234, MMIO::Constant<u8>(0x42), MMIO::Nop<u8>());
+	m_mapping->Register(0xCC001234, MMIO::Constant<u16>(0x1234), MMIO::Nop<u16>());
+	m_mapping->Register(0xCC001234, MMIO::Constant<u32>(0xdeadbeef), MMIO::Nop<u32>());
+
+	u8 val8;   m_mapping->Read(0xCC001234, &val8);
+	u16 val16; m_mapping->Read(0xCC001234, &val16);
+	u32 val32; m_mapping->Read(0xCC001234, &val32);
+
+	EXPECT_EQ(0x42, val8);
+	EXPECT_EQ(0x1234, val16);
+	EXPECT_EQ(0xdeadbeef, val32);
+}
+
+TEST_F(MappingTest, ReadWriteDirect)
+{
+	u8 target_8 = 0;
+	u16 target_16 = 0;
+	u32 target_32 = 0;
+
+	m_mapping->Register(0xCC001234, MMIO::DirectRead<u8>(&target_8), MMIO::DirectWrite<u8>(&target_8));
+	m_mapping->Register(0xCC001234, MMIO::DirectRead<u16>(&target_16), MMIO::DirectWrite<u16>(&target_16));
+	m_mapping->Register(0xCC001234, MMIO::DirectRead<u32>(&target_32), MMIO::DirectWrite<u32>(&target_32));
+
+	for (int i = 0; i < 100; ++i)
+	{
+		u8 val8;   m_mapping->Read(0xCC001234, &val8);  EXPECT_EQ(i, val8);
+		u16 val16; m_mapping->Read(0xCC001234, &val16); EXPECT_EQ(i, val16);
+		u32 val32; m_mapping->Read(0xCC001234, &val32); EXPECT_EQ(i, val32);
+
+		val8 += 1; m_mapping->Write(0xCC001234, val8);
+		val16 += 1; m_mapping->Write(0xCC001234, val16);
+		val32 += 1; m_mapping->Write(0xCC001234, val32);
+	}
+}