diff --git a/README.md b/README.md
index 035fd0b..b6a4b86 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,10 @@
 go-addr-util
 ==================
 
-[![](https://img.shields.io/badge/made%20by-Protocol%20Labs-blue.svg?style=flat-square)](http://ipn.io)
-[![](https://img.shields.io/badge/project-libp2p-blue.svg?style=flat-square)](http://github.com/libp2p/libp2p)
-[![](https://img.shields.io/badge/freenode-%23ipfs-blue.svg?style=flat-square)](http://webchat.freenode.net/?channels=%23ipfs)
-[![Coverage Status](https://coveralls.io/repos/github/libp2p/go-addr-util/badge.svg?branch=master)](https://coveralls.io/github/libp2p/go-addr-util?branch=master)
+[![](https://img.shields.io/badge/made%20by-Protocol%20Labs-blue.svg?style=flat-square)](http://protocol.ai)
+[![](https://img.shields.io/badge/project-libp2p-blue.svg?style=flat-square)](http://libp2p.io/)
+[![](https://img.shields.io/badge/freenode-%23libp2p-blue.svg?style=flat-square)](http://webchat.freenode.net/?channels=%23libp2p)
+[![codecov](https://codecov.io/gh/libp2p/go-addr-util/branch/master/graph/badge.svg)](https://codecov.io/gh/libp2p/go-addr-util)
 [![Travis CI](https://travis-ci.org/libp2p/go-addr-util.svg?branch=master)](https://travis-ci.org/libp2p/go-addr-util)
 
 > Address utilities for libp2p swarm.
diff --git a/addr.go b/addr.go
index f27e5b7..3a922a6 100644
--- a/addr.go
+++ b/addr.go
@@ -11,8 +11,8 @@ import (
 
 var log = logging.Logger("addrutil")
 
-// FilterAddrs is a filter that removes certain addresses, according the given filters.
-// if all filters return true, the address is kept.
+// FilterAddrs is a filter that removes certain addresses, according to the given filters.
+// If all filters return true, the address is kept.
 func FilterAddrs(a []ma.Multiaddr, filters ...func(ma.Multiaddr) bool) []ma.Multiaddr {
 	b := make([]ma.Multiaddr, 0, len(a))
 	for _, addr := range a {
diff --git a/addr_test.go b/addr_test.go
index e071468..3707ad6 100644
--- a/addr_test.go
+++ b/addr_test.go
@@ -1,10 +1,9 @@
 package addrutil
 
 import (
-	"testing"
-
 	ma "github.com/multiformats/go-multiaddr"
 	manet "github.com/multiformats/go-multiaddr-net"
+	"testing"
 )
 
 func newMultiaddr(t *testing.T, s string) ma.Multiaddr {
@@ -17,10 +16,10 @@ func newMultiaddr(t *testing.T, s string) ma.Multiaddr {
 }
 
 func TestFilterAddrs(t *testing.T) {
-
 	bad := []ma.Multiaddr{
 		newMultiaddr(t, "/ip6/fe80::1/tcp/1234"),   // link local
 		newMultiaddr(t, "/ip6/fe80::100/tcp/1234"), // link local
+		newMultiaddr(t, ""),
 	}
 
 	good := []ma.Multiaddr{
@@ -211,3 +210,26 @@ func TestSubtract(t *testing.T) {
 		}
 	}
 }
+
+func TestAddrInList(t *testing.T) {
+	addrs := []ma.Multiaddr{
+		newMultiaddr(t, "/ip4/0.0.0.0/tcp/1234"),
+		newMultiaddr(t, "/ip6/::/tcp/1234"),
+		newMultiaddr(t, "/ip6/fe80::/tcp/1234"),
+	}
+	if in := AddrInList(newMultiaddr(t, "/ip6/fe80::1/tcp/1234"), addrs); in {
+		t.Errorf("Expected address %s to not be in list", "/ip6/fe80::1/tcp/1234")
+	}
+	if in := AddrInList(newMultiaddr(t, "/ip4/0.0.0.0/tcp/1234"), addrs); !in {
+		t.Errorf("Expected address %s to be in list", "/ip4/0.0.0.0/tcp/1234")
+	}
+}
+
+func TestCheckNATWarning(t *testing.T) {
+	multiAddr := newMultiaddr(t, "/ip4/0.0.0.0/tcp/1234")
+	listen := []ma.Multiaddr{
+		multiAddr,
+	}
+	CheckNATWarning(multiAddr, multiAddr, listen)
+	CheckNATWarning(newMultiaddr(t, "/ip6/fe80::/tcp/1234"), multiAddr, listen)
+}
diff --git a/filter_test.go b/filter_test.go
new file mode 100644
index 0000000..d5f57d1
--- /dev/null
+++ b/filter_test.go
@@ -0,0 +1,37 @@
+package addrutil
+
+import (
+	ma "github.com/multiformats/go-multiaddr"
+	"testing"
+)
+
+func TestSubtractAndNegFilter(t *testing.T) {
+	localhost := newMultiaddr(t, "/ip4/127.0.0.1/tcp/1234")
+	private := newMultiaddr(t, "/ip4/192.168.1.1/tcp/1234")
+	toRemoveFilter := SubtractFilter(
+		localhost,
+		newMultiaddr(t, "/ip6/::1/tcp/1234"),
+		newMultiaddr(t, "/ip4/1.2.3.4/udp/1234/utp"),
+	)
+	result := FilterAddrs([]ma.Multiaddr{localhost, private}, toRemoveFilter)
+	if len(result) != 1 || !result[0].Equal(private) {
+		t.Errorf("Expected only one remaining address: %s", private.String())
+	}
+
+	// Negate original filter
+	result = FilterAddrs([]ma.Multiaddr{localhost, private}, FilterNeg(toRemoveFilter))
+	if len(result) != 1 || !result[0].Equal(localhost) {
+		t.Errorf("Expected only one remaining address: %s", localhost.String())
+	}
+}
+
+func TestIsFDCostlyTransport(t *testing.T) {
+	tcpMa := newMultiaddr(t, "/ip4/127.0.0.1/tcp/1234")
+	if ok := IsFDCostlyTransport(tcpMa); !ok {
+		t.Errorf("Expected address %s to need a new file descriptor per new connection", tcpMa.String())
+	}
+	udpMa := newMultiaddr(t, "/ip4/127.0.0.1/udp/1234")
+	if ok := IsFDCostlyTransport(udpMa); ok {
+		t.Errorf("Expected address %s to not need a new file descriptor per new connection", udpMa.String())
+	}
+}