diff --git a/.drone.yml b/.drone.yml
index b377ea8..1e5495a 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -13,13 +13,12 @@ steps:
     - pull_request
     - tag
 
-# steps:
-# - name: test-unit
-#   image: docker.io/volkerraschek/build-image:latest
-#   commands:
-#   - make test/unit
-#   when:
-#     event:
-#     - push
-#     - pull_request
-#     - tag
\ No newline at end of file
+- name: test-unit
+  image: docker.io/volkerraschek/build-image:latest
+  commands:
+  - make test/unit
+  when:
+    event:
+    - push
+    - pull_request
+    - tag
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index c5e82d7..43e5476 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-bin
\ No newline at end of file
+bin
+coverage.txt
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 1ecaee0..13779b9 100644
--- a/Makefile
+++ b/Makefile
@@ -64,6 +64,15 @@ PHONY+=clean
 clean:
 	-rm --force --recursive bin/
 
+# TEST
+# ==============================================================================
+PHONY+=test/unit
+test/unit:
+	go test -v -race -coverprofile=coverage.txt -covermode=atomic -timeout 600s -count=1 ./...
+
+test/coverage: test/unit
+	go tool cover -html=coverage.txt
+
 # PHONY
 # ==============================================================================
 # Declare the contents of the PHONY variable as phony.  We keep that information
diff --git a/go.mod b/go.mod
index d5fda50..c95b914 100644
--- a/go.mod
+++ b/go.mod
@@ -5,4 +5,5 @@ go 1.15
 require (
 	git.cryptic.systems/volker.raschek/go-logger v0.1.0
 	github.com/spf13/cobra v1.0.0
+	github.com/stretchr/testify v1.6.1
 )
diff --git a/go.sum b/go.sum
index a52fb95..8d8cfb9 100644
--- a/go.sum
+++ b/go.sum
@@ -17,6 +17,7 @@ github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
@@ -59,6 +60,7 @@ github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRW
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v0.9.3/go.mod h1:/TN21ttK/J9q6uSwhBd54HahCDft0ttaMvbicHlPoso=
@@ -87,6 +89,7 @@ github.com/spf13/viper v1.4.0/go.mod h1:PTJ7Z/lr49W6bUbkmS1V3by4uWynFiR9p7+dSq/y
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
 github.com/ugorji/go v1.1.4/go.mod h1:uQMGLiO92mf5W77hV/PUCpI3pbzQx3CRekS0kk+RGrc=
@@ -130,5 +133,6 @@ gopkg.in/resty.v1 v1.12.0/go.mod h1:mDo4pnntr5jdWRML875a/NmxYqAlA73dVijT2AXvQQo=
 gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
diff --git a/main.go b/main.go
index 1f5e6ed..6a81205 100644
--- a/main.go
+++ b/main.go
@@ -127,14 +127,20 @@ Loop:
 }
 
 func removeSSHKeys(sshKeys []*sshKey, removeSSHKeys []*sshKey) []*sshKey {
-	for i := range removeSSHKeys {
-		for j := range sshKeys {
-			if sshKeys[j].Compare(removeSSHKeys[i]) {
-				sshKeys = append(sshKeys[:j], sshKeys[j+1:]...)
+
+	s := make([]*sshKey, 0)
+
+Loop:
+	for i := range sshKeys {
+		for j := range removeSSHKeys {
+			if sshKeys[i].Compare(removeSSHKeys[j]) {
+				continue Loop
 			}
 		}
+		s = append(s, sshKeys[i])
 	}
-	return sshKeys
+
+	return s
 }
 
 func rootCmd(cmd *cobra.Command, args []string) error {
@@ -210,11 +216,7 @@ func writeSSHKeys(authorizedKeyFile string, sshKeys []*sshKey) error {
 	}
 
 	for i := range sshKeys {
-		if len(sshKeys[i].alias) > 0 {
-			fmt.Fprintf(f, "%v %v %v\n", sshKeys[i].algorithm, sshKeys[i].pubKey, sshKeys[i].alias)
-		} else {
-			fmt.Fprintf(f, "%v %v\n", sshKeys[i].algorithm, sshKeys[i].pubKey)
-		}
+		fmt.Fprintln(f, sshKeys[i].String())
 	}
 
 	return nil
@@ -240,6 +242,14 @@ func (s *sshKey) SetAlias(alias string) {
 	}
 }
 
+func (s *sshKey) String() string {
+	l := fmt.Sprintf("%v %v", s.algorithm, s.pubKey)
+	if len(s.alias) > 0 {
+		l = fmt.Sprintf("%v %v", l, s.alias)
+	}
+	return l
+}
+
 func (s *sshKey) Validate() error {
 	entries := map[string]string{
 		"algorithm": s.algorithm,
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..92737e7
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,58 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRemove(t *testing.T) {
+	require := require.New(t)
+
+	s := []*sshKey{
+		{algorithm: "ssh-ed25519", pubKey: "sdfsdf", alias: "hello@world"},
+		{algorithm: "ssh-rsa", pubKey: "asdfasdadsad", alias: "world@hello"},
+	}
+
+	r := []*sshKey{
+		{algorithm: "ssh-ed25519", pubKey: "sdfsdf", alias: "hello@world"},
+	}
+
+	result := removeSSHKeys(s, r)
+	require.Len(result, 1)
+
+	r = []*sshKey{
+		{algorithm: "ssh-ed25519", pubKey: "sdfsdf", alias: "hello@world"},
+		{algorithm: "ssh-rsa", pubKey: "asdfasdadsad", alias: "world@hello"},
+	}
+
+	result = removeSSHKeys(s, r)
+	require.Len(result, 0)
+
+	r = []*sshKey{
+		{algorithm: "ssh-ed25519", pubKey: "sdfsdf"},
+	}
+
+	result = removeSSHKeys(s, r)
+	require.Len(result, 1)
+}
+
+func TestSSHKeyString(t *testing.T) {
+	require := require.New(t)
+
+	s := []*sshKey{
+		{algorithm: "ssh-ed25519", pubKey: "sdfsdf", alias: "hello@world"},
+		{algorithm: "ssh-rsa", pubKey: "asdfasdadsad", alias: "world@hello"},
+		{algorithm: "ssh-rsa", pubKey: "asdfasdsdfsfadsad"},
+	}
+
+	b := []string{
+		"ssh-ed25519 sdfsdf hello@world",
+		"ssh-rsa asdfasdadsad world@hello",
+		"ssh-rsa asdfasdsdfsfadsad",
+	}
+
+	for i := range s {
+		require.Equal(b[i], s[i].String())
+	}
+}