diff --git a/envdef.go b/envdef.go
index 4cef835..e1712f2 100644
--- a/envdef.go
+++ b/envdef.go
@@ -7,12 +7,10 @@ import (
 )
 
 func Diff(source, dist string, overwrite bool) (*Result, error) {
-	var (
-		insertSlice   InsertSlice
-		updateSlice   UpdateSlice
-		deleteSlice   DeleteSlice
-		noChangeSlice NoChangeSlice
-	)
+	insertSlice := InsertSlice{}
+	updateSlice := UpdateSlice{}
+	deleteSlice := DeleteSlice{}
+	noChangeSlice := NoChangeSlice{}
 
 	sourceEnv, err := Read(source)
 	if err != nil {
@@ -27,18 +25,16 @@ func Diff(source, dist string, overwrite bool) (*Result, error) {
 	for k, v := range sourceEnv {
 		// update
 		if _, ok := distEnv[k]; ok {
-			if v == distEnv[k] {
-				// nochange
+			// nochange
+			if !overwrite || v == distEnv[k] {
 				noChangeSlice = append(noChangeSlice, envFormat(k, v))
 				continue
 			}
 
-			if overwrite {
+			if v != distEnv[k] {
 				updateSlice = append(updateSlice, envFormat(k, v))
-			} else {
-				updateSlice = append(updateSlice, envFormat(k, distEnv[k]))
+				continue
 			}
-			continue
 		}
 
 		// insert
diff --git a/envdef_test.go b/envdef_test.go
index a561878..33c367c 100644
--- a/envdef_test.go
+++ b/envdef_test.go
@@ -1,8 +1,9 @@
 package envdef
 
 import (
-	"reflect"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestRead(t *testing.T) {
@@ -62,47 +63,19 @@ func TestDiff(t *testing.T) {
 			overwrite: false,
 			expected: Result{
 				InsertSlice:   InsertSlice{"INSERT=insert"},
-				UpdateSlice:   UpdateSlice{"UPDATE=update"},
+				UpdateSlice:   UpdateSlice{},
 				DeleteSlice:   DeleteSlice{"DELETE=delete"},
-				NoChangeSlice: NoChangeSlice{"NOCHANGE=nochange"},
+				NoChangeSlice: NoChangeSlice{"UPDATE=default", "NOCHANGE=nochange"},
 			},
 		},
 	}
 
 	for _, d := range testdata {
 		res, _ := Diff(d.source, d.dist, d.overwrite)
-		// check len
 
-		if len(d.expected.InsertSlice) != len(res.InsertSlice) {
-			t.Errorf("expected len(%v), got len(%v)", len(d.expected.InsertSlice), len(res.InsertSlice))
-		}
-
-		if len(d.expected.UpdateSlice) != len(res.UpdateSlice) {
-			t.Errorf("expected len(%v), got len(%v)", len(d.expected.UpdateSlice), len(res.UpdateSlice))
-		}
-
-		if len(d.expected.DeleteSlice) != len(res.DeleteSlice) {
-			t.Errorf("expected len(%v), got len(%v)", len(d.expected.DeleteSlice), len(res.DeleteSlice))
-		}
-
-		if len(d.expected.NoChangeSlice) != len(res.NoChangeSlice) {
-			t.Errorf("expected len(%v), got len(%v)", len(d.expected.NoChangeSlice), len(res.NoChangeSlice))
-		}
-
-		if !reflect.DeepEqual(d.expected.InsertSlice, res.InsertSlice) {
-			t.Errorf("expected %s, got %s", d.expected.InsertSlice, res.InsertSlice)
-		}
-
-		if !reflect.DeepEqual(d.expected.UpdateSlice, res.UpdateSlice) {
-			t.Errorf("expected %s, got %s", d.expected.UpdateSlice, res.UpdateSlice)
-		}
-
-		if !reflect.DeepEqual(d.expected.DeleteSlice, res.DeleteSlice) {
-			t.Errorf("expected %s, got %s", d.expected.DeleteSlice, res.DeleteSlice)
-		}
-
-		if !reflect.DeepEqual(d.expected.NoChangeSlice, res.NoChangeSlice) {
-			t.Errorf("expected %s, got %s", d.expected.NoChangeSlice, res.NoChangeSlice)
-		}
+		assert.ElementsMatch(t, d.expected.InsertSlice, res.InsertSlice)
+		assert.ElementsMatch(t, d.expected.UpdateSlice, res.UpdateSlice)
+		assert.ElementsMatch(t, d.expected.DeleteSlice, res.DeleteSlice)
+		assert.ElementsMatch(t, d.expected.NoChangeSlice, res.NoChangeSlice)
 	}
 }
diff --git a/go.mod b/go.mod
index 8c98b21..8b3d988 100644
--- a/go.mod
+++ b/go.mod
@@ -6,5 +6,6 @@ require (
 	github.com/fatih/color v1.9.0
 	github.com/joho/godotenv v1.3.0
 	github.com/mattn/go-colorable v0.1.6 // indirect
-	golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527 // indirect
+	github.com/stretchr/testify v1.5.1
+	golang.org/x/sys v0.0.0-20200316230553-a7d97aace0b0 // indirect
 )
diff --git a/go.sum b/go.sum
index aa6b300..968799c 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fatih/color v1.9.0 h1:8xPHl4/q1VyqGIPif1F+1V3Y3lSmrq01EabUW3CoW5s=
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
 github.com/joho/godotenv v1.3.0 h1:Zjp+RcGpHhGlrMbJzXTrZZPrWj+1vfm90La1wgB6Bhc=
@@ -9,10 +11,20 @@ github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hd
 github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
+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/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
+github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae h1:/WDfKMnPU+m5M4xB+6x4kaepxRw6jWvR5iDRdvjHgy8=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527 h1:uYVVQ9WP/Ds2ROhcaGPeIdVq0RIXVLwsHlnvJ+cT1So=
-golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200316230553-a7d97aace0b0 h1:4Khi5GeNOkZS5DqSBRn4Sy7BE6GuxwOqARPqfurkdNk=
+golang.org/x/sys v0.0.0-20200316230553-a7d97aace0b0/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=