diff --git a/test/net/addr/subnet.cpp b/test/net/addr/subnet.cpp
new file mode 100644
index 0000000..561507c
--- /dev/null
+++ b/test/net/addr/subnet.cpp
@@ -0,0 +1,160 @@
+#include <fmt/format.h>
+
+#include <stdplus/net/addr/subnet.hpp>
+
+#include <gtest/gtest.h>
+
+namespace stdplus
+{
+
+auto addr4Full = In4Addr{255, 255, 255, 255};
+auto addr6Full = In6Addr{255, 255, 255, 255, 255, 255, 255, 255,
+                         255, 255, 255, 255, 255, 255, 255, 255};
+
+TEST(Subnet4, Basic)
+{
+    EXPECT_NO_THROW(Subnet4(in_addr{0xffffffff}, 32));
+    EXPECT_NO_THROW(Subnet4(addr4Full, 0));
+    EXPECT_NO_THROW(Subnet4(in_addr{}, 10));
+    EXPECT_THROW(Subnet4(in_addr{0xffffffff}, 33), std::invalid_argument);
+    EXPECT_THROW(Subnet4(in_addr{0xffffffff}, 64), std::invalid_argument);
+
+    EXPECT_NE(Subnet4(in_addr{0xff}, 32), Subnet4(in_addr{}, 32));
+    EXPECT_NE(Subnet4(in_addr{0xff}, 26), Subnet4(in_addr{0xff}, 27));
+    EXPECT_EQ(Subnet4(in_addr{0xff}, 32), Subnet4(in_addr{0xff}, 32));
+    EXPECT_EQ(Subnet4(in_addr{}, 1), Subnet4(in_addr{}, 1));
+}
+
+TEST(Subnet4, Network)
+{
+    EXPECT_EQ((In4Addr{}), Subnet4(In4Addr{}, 32).network());
+    EXPECT_EQ(addr4Full, Subnet4(addr4Full, 32).network());
+    EXPECT_EQ((In4Addr{255, 255, 128, 0}), Subnet4(addr4Full, 17).network());
+    EXPECT_EQ((In4Addr{255, 255, 0, 0}), Subnet4(addr4Full, 16).network());
+    EXPECT_EQ((In4Addr{255, 254, 0, 0}), Subnet4(addr4Full, 15).network());
+    EXPECT_EQ((In4Addr{}), Subnet4(addr4Full, 0).network());
+    EXPECT_EQ((In4Addr{}), Subnet4(In4Addr{}, 0).network());
+}
+
+TEST(Subnet4, Contains)
+{
+    EXPECT_TRUE(Subnet4(addr4Full, 32).contains(addr4Full));
+    EXPECT_FALSE(Subnet4(addr4Full, 32).contains(In4Addr{255, 255, 255, 254}));
+    EXPECT_FALSE(Subnet4(addr4Full, 32).contains(In4Addr{}));
+    EXPECT_TRUE(
+        Subnet4(addr4Full, 17).contains(static_cast<in_addr>(addr4Full)));
+    EXPECT_TRUE(Subnet4(addr4Full, 17).contains(In4Addr{255, 255, 128, 134}));
+    EXPECT_FALSE(Subnet4(addr4Full, 17).contains(In4Addr{255, 255, 127, 132}));
+    EXPECT_TRUE(Subnet4(addr4Full, 14).contains(addr4Full));
+    EXPECT_TRUE(Subnet4(addr4Full, 0).contains(addr4Full));
+    EXPECT_TRUE(Subnet4(In4Addr{}, 0).contains(addr4Full));
+    EXPECT_TRUE(Subnet4(addr4Full, 0).contains(In4Addr{}));
+}
+
+TEST(Subnet6, Basic)
+{
+    EXPECT_NO_THROW(Subnet6(in6_addr{0xff}, 128));
+    EXPECT_NO_THROW(Subnet6(addr6Full, 0));
+    EXPECT_NO_THROW(Subnet6(in6_addr{}, 65));
+    EXPECT_THROW(Subnet6(in6_addr{0xff}, 129), std::invalid_argument);
+    EXPECT_THROW(Subnet6(in6_addr{0xff}, 150), std::invalid_argument);
+
+    EXPECT_NE(Subnet6(in6_addr{0xff}, 32), Subnet6(in6_addr{}, 32));
+    EXPECT_NE(Subnet6(in6_addr{0xff}, 26), Subnet6(in6_addr{0xff}, 27));
+    EXPECT_EQ(Subnet6(in6_addr{0xff}, 32), Subnet6(in6_addr{0xff}, 32));
+    EXPECT_EQ(Subnet6(in6_addr{}, 1), Subnet6(in6_addr{}, 1));
+}
+
+TEST(Subnet6, Network)
+{
+    EXPECT_EQ(In6Addr(), Subnet6(In6Addr(), 128).network());
+    EXPECT_EQ(addr6Full, Subnet6(addr6Full, 128).network());
+    EXPECT_EQ((In6Addr{255, 255, 255, 255, 224}),
+              Subnet6(addr6Full, 35).network());
+    EXPECT_EQ((In6Addr{255, 255, 255, 255}), Subnet6(addr6Full, 32).network());
+    EXPECT_EQ((In6Addr{255, 255, 128, 0}), Subnet6(addr6Full, 17).network());
+    EXPECT_EQ((In6Addr{255, 255, 0, 0}), Subnet6(addr6Full, 16).network());
+    EXPECT_EQ((In6Addr{255, 254, 0, 0}), Subnet6(addr6Full, 15).network());
+    EXPECT_EQ((In6Addr{}), Subnet6(addr6Full, 0).network());
+    EXPECT_EQ((In6Addr{}), Subnet6(In6Addr{}, 0).network());
+}
+
+TEST(Subnet6, Contains)
+{
+    auto addr6NFull = addr6Full;
+    addr6NFull.s6_addr[15] = 254;
+    EXPECT_TRUE(Subnet6(addr6Full, 128).contains(addr6Full));
+    EXPECT_FALSE(Subnet6(addr6Full, 128).contains(addr6NFull));
+    EXPECT_FALSE(Subnet6(addr6Full, 128).contains(In6Addr{}));
+    EXPECT_TRUE(
+        Subnet6(addr6Full, 127).contains(static_cast<in6_addr>(addr6Full)));
+    EXPECT_TRUE(Subnet6(addr6Full, 127).contains(addr6NFull));
+    EXPECT_TRUE(
+        Subnet6(addr6Full, 33).contains(In6Addr{255, 255, 255, 255, 128, 255}));
+    EXPECT_FALSE(
+        Subnet6(addr6Full, 33).contains(In6Addr{255, 255, 255, 255, 127}));
+    EXPECT_TRUE(Subnet6(In6Addr{}, 33).contains(In6Addr{0, 0, 0, 0, 127}));
+    EXPECT_TRUE(
+        Subnet6(addr6Full, 14).contains(In6Addr{255, 255, 0, 0, 0, 0, 0, 145}));
+    EXPECT_FALSE(Subnet6(addr6Full, 14).contains(In6Addr{255, 127, 1}));
+    EXPECT_TRUE(Subnet6(addr6Full, 0).contains(addr6Full));
+    EXPECT_TRUE(Subnet6(In6Addr{}, 0).contains(addr6Full));
+    EXPECT_TRUE(Subnet6(addr6Full, 0).contains(In6Addr{}));
+}
+
+TEST(SubnetAny, Basic)
+{
+    EXPECT_NO_THROW(SubnetAny(in_addr{0xffffffff}, 32));
+    EXPECT_NO_THROW(SubnetAny(addr4Full, 0));
+    EXPECT_NO_THROW(SubnetAny(InAnyAddr{addr4Full}, 0));
+    EXPECT_NO_THROW(SubnetAny(in_addr{}, 10));
+    EXPECT_THROW(SubnetAny(in_addr{0xffffffff}, 33), std::invalid_argument);
+    EXPECT_THROW(SubnetAny(InAnyAddr{in_addr{0xffffffff}}, 33),
+                 std::invalid_argument);
+    EXPECT_THROW(SubnetAny(in_addr{0xffffffff}, 64), std::invalid_argument);
+    EXPECT_NO_THROW(SubnetAny(in6_addr{0xff}, 128));
+    EXPECT_NO_THROW(SubnetAny(addr6Full, 0));
+    EXPECT_NO_THROW(SubnetAny(InAnyAddr{addr6Full}, 0));
+    EXPECT_NO_THROW(SubnetAny(in6_addr{}, 65));
+    EXPECT_THROW(SubnetAny(in6_addr{0xff}, 129), std::invalid_argument);
+    EXPECT_THROW(SubnetAny(InAnyAddr{in6_addr{0xff}}, 129),
+                 std::invalid_argument);
+    EXPECT_THROW(SubnetAny(in6_addr{0xff}, 150), std::invalid_argument);
+
+    EXPECT_NO_THROW(SubnetAny(Subnet4(in_addr{}, 32)));
+    EXPECT_NO_THROW(SubnetAny(Subnet6(in6_addr{0xff}, 128)));
+
+    EXPECT_NE(SubnetAny(in6_addr{0xff}, 32), Subnet6(in6_addr{}, 32));
+    EXPECT_NE(Subnet6(in6_addr{0xff}, 26), SubnetAny(in6_addr{0xff}, 27));
+    EXPECT_EQ(SubnetAny(in6_addr{0xff}, 32), Subnet6(in6_addr{0xff}, 32));
+    EXPECT_EQ(SubnetAny(in6_addr{0xff}, 32), SubnetAny(in6_addr{0xff}, 32));
+    EXPECT_NE(SubnetAny(in6_addr{0xff}, 32), Subnet4(in_addr{0xff}, 32));
+    EXPECT_NE(SubnetAny(in_addr{0xff}, 32), Subnet4(in_addr{}, 32));
+    EXPECT_NE(Subnet4(in_addr{0xff}, 26), SubnetAny(in_addr{0xff}, 27));
+    EXPECT_EQ(SubnetAny(in_addr{0xff}, 32), Subnet4(in_addr{0xff}, 32));
+    EXPECT_EQ(SubnetAny(in_addr{0xff}, 32), SubnetAny(in_addr{0xff}, 32));
+}
+
+TEST(SubnetAny, Network)
+{
+    EXPECT_EQ(In6Addr(), SubnetAny(In6Addr(), 128).network());
+    EXPECT_EQ(addr6Full, SubnetAny(addr6Full, 128).network());
+    EXPECT_EQ(In6Addr(), SubnetAny(addr6Full, 0).network());
+    EXPECT_EQ(In4Addr(), SubnetAny(In4Addr(), 32).network());
+    EXPECT_EQ(addr4Full, SubnetAny(addr4Full, 32).network());
+    EXPECT_EQ(In4Addr(), SubnetAny(addr4Full, 0).network());
+}
+
+TEST(SubnetAny, Contains)
+{
+    EXPECT_TRUE(SubnetAny(addr6Full, 128).contains(addr6Full));
+    EXPECT_TRUE(SubnetAny(addr6Full, 128).contains(InAnyAddr{addr6Full}));
+    EXPECT_FALSE(SubnetAny(addr6Full, 128).contains(in6_addr{}));
+    EXPECT_FALSE(SubnetAny(addr6Full, 128).contains(InAnyAddr(in6_addr{})));
+    EXPECT_TRUE(SubnetAny(addr4Full, 32).contains(addr4Full));
+    EXPECT_TRUE(SubnetAny(addr4Full, 32).contains(InAnyAddr{addr4Full}));
+    EXPECT_FALSE(SubnetAny(addr4Full, 32).contains(in_addr{}));
+    EXPECT_FALSE(SubnetAny(addr4Full, 32).contains(InAnyAddr{In4Addr{}}));
+}
+
+} // namespace stdplus