diff --git a/.gitignore b/.gitignore
index 059c35d..515eb78 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,7 +5,6 @@
 *.so
 *.dylib
 wesher
-wg
 
 # Test binary, build with `go test -c`
 *.test
diff --git a/tests/wg b/tests/wg
new file mode 100755
index 0000000..bb95c6f
--- /dev/null
+++ b/tests/wg
@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# docker run --rm -it --hostname test3 --name test3 --network wesher_test --volume `pwd`:/app golang:1.12-alpine
+# cd /app
+# apk add git
+# export PATH=/app:$PATH
+# go run . --loglevel debug --clusterkey 'ILICZ3yBMCGAWNIq5Pn0bewBVimW3Q2yRVJ/Be+b1Uc='
+
+case $1 in
+    genkey)
+        echo "ILICZ3yBMCGAWNIq5Pn0bewBVimW3Q2yRVJ/Be+b1Uc="
+        ;;
+    pubkey)
+        read x
+        echo "VceweY6x/QdGXEQ6frXrSd8CwUAInUmqIc6G/qi8FHo="
+        ;;
+    *)
+        ;;
+esac
\ No newline at end of file
diff --git a/wireguard.go b/wireguard.go
index 3ef2b5c..bd4b7b7 100644
--- a/wireguard.go
+++ b/wireguard.go
@@ -1,8 +1,8 @@
 package main
 
 import (
-	"crypto/md5"
 	"fmt"
+	"hash/fnv"
 	"net"
 	"os"
 	"os/exec"
@@ -33,8 +33,11 @@ type wgState struct {
 	PubKey      string
 }
 
+var wgPath = "wg"
+var wgQuickPath = "wg-quick"
+
 func newWGConfig(iface string, port int) (*wgState, error) {
-	if err := exec.Command("wg").Run(); err != nil {
+	if err := exec.Command(wgPath).Run(); err != nil {
 		return nil, fmt.Errorf("could not exec wireguard: %s", err)
 	}
 
@@ -54,16 +57,18 @@ func newWGConfig(iface string, port int) (*wgState, error) {
 
 func (wg *wgState) assignOverlayAddr(ipnet *net.IPNet, name string) {
 	// TODO: this is way too brittle and opaque
-	ip := []byte(ipnet.IP)
 	bits, size := ipnet.Mask.Size()
+	ip := make([]byte, net.IPv6len)
+	copy(ip, []byte(ipnet.IP))
 
-	h := md5.New()
+	h := fnv.New128a()
 	h.Write([]byte(name))
 	hb := h.Sum(nil)
 
-	for i := 0; i < (size-bits)/8; i++ {
-		ip[size/8-i-1] = hb[i]
+	for i := 1; i <= (size-bits)/8; i++ {
+		ip[len(ip)-i] = hb[len(hb)-i]
 	}
+
 	wg.OverlayAddr = net.IP(ip)
 }
 
@@ -84,25 +89,25 @@ func (wg *wgState) writeConf(nodes []node) error {
 }
 
 func (wg *wgState) downInterface() error {
-	if err := exec.Command("wg", "show", wg.iface).Run(); err != nil {
+	if err := exec.Command(wgPath, "show", wg.iface).Run(); err != nil {
 		return nil // assume a failure means the interface is not there
 	}
-	return exec.Command("wg-quick", "down", wg.iface).Run()
+	return exec.Command(wgQuickPath, "down", wg.iface).Run()
 }
 
 func (wg *wgState) upInterface() error {
-	return exec.Command("wg-quick", "up", wg.iface).Run()
+	return exec.Command(wgQuickPath, "up", wg.iface).Run()
 }
 
 func wgKeyPair() (string, string, error) {
-	cmd := exec.Command("wg", "genkey")
+	cmd := exec.Command(wgPath, "genkey")
 	outPriv := strings.Builder{}
 	cmd.Stdout = &outPriv
 	if err := cmd.Run(); err != nil {
 		return "", "", err
 	}
 
-	cmd = exec.Command("wg", "pubkey")
+	cmd = exec.Command(wgPath, "pubkey")
 	outPub := strings.Builder{}
 	cmd.Stdout = &outPub
 	cmd.Stdin = strings.NewReader(outPriv.String())
diff --git a/wireguard_test.go b/wireguard_test.go
new file mode 100644
index 0000000..7f71d1b
--- /dev/null
+++ b/wireguard_test.go
@@ -0,0 +1,87 @@
+package main
+
+import (
+	"net"
+	"reflect"
+	"testing"
+)
+
+func init() {
+	wgPath = "tests/wg"
+	wgQuickPath = "tests/wg-quick"
+}
+
+func Test_wgKeyPair(t *testing.T) {
+	tests := []struct {
+		name    string
+		want    string
+		want1   string
+		wantErr bool
+	}{
+		// see tests/wg for values
+		{"generate fixed values", "ILICZ3yBMCGAWNIq5Pn0bewBVimW3Q2yRVJ/Be+b1Uc=", "VceweY6x/QdGXEQ6frXrSd8CwUAInUmqIc6G/qi8FHo=", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, got1, err := wgKeyPair()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("wgKeyPair() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("wgKeyPair() got = %v, want %v", got, tt.want)
+			}
+			if got1 != tt.want1 {
+				t.Errorf("wgKeyPair() got1 = %v, want %v", got1, tt.want1)
+			}
+		})
+	}
+}
+
+func Test_wgState_assignOverlayAddr(t *testing.T) {
+	type args struct {
+		ipnet *net.IPNet
+		name  string
+	}
+	tests := []struct {
+		name string
+		args args
+		want net.IP
+	}{
+		{
+			"assign in big ipv4 net",
+			args{&net.IPNet{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(8, 32)}, "test"},
+			net.ParseIP("10.221.153.165"), // if we ever have to change this, we should probably also mark it as a breaking change
+		},
+		{
+			"assign in ipv6 net",
+			args{&net.IPNet{IP: net.ParseIP("2001:db8::"), Mask: net.CIDRMask(32, 128)}, "test"},
+			net.ParseIP("2001:db8:c575:7277:b806:e994:13dd:99a5"), // if we ever have to change this, we should probably also mark it as a breaking change
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			wg := &wgState{}
+			wg.assignOverlayAddr(tt.args.ipnet, tt.args.name)
+
+			if !reflect.DeepEqual(wg.OverlayAddr, tt.want) {
+				t.Errorf("assignOverlayAddr() set = %s, want %s", wg.OverlayAddr, tt.want)
+			}
+		})
+	}
+}
+
+// This is just to ensure - if we ever change the hashing function - that it spreads the results in a way that at least
+// avoids the most obvious collisions.
+func Test_wgState_assignOverlayAddr_no_obvious_collisions(t *testing.T) {
+	ipnet := &net.IPNet{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(24, 32)}
+	assignments := make(map[string]string)
+	for _, n := range []string{"test", "test1", "test2", "1test", "2test"} {
+		wg := &wgState{}
+		wg.assignOverlayAddr(ipnet, n)
+		if assigned, ok := assignments[wg.OverlayAddr.String()]; ok {
+			t.Errorf("IP assignment collision: hash(%s) = hash(%s)", n, assigned)
+		}
+		assignments[wg.OverlayAddr.String()] = n
+	}
+}