diff --git a/go.mod b/go.mod
index 2838ddc..132165e 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module github.com/6543/go-hexcolor
 
 go 1.15
+
+require github.com/stretchr/testify v1.6.1
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..56d62e7
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,10 @@
+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/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/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+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=
diff --git a/hexcolor_test.go b/hexcolor_test.go
new file mode 100644
index 0000000..ac2e3cb
--- /dev/null
+++ b/hexcolor_test.go
@@ -0,0 +1,32 @@
+package go_hexcolor
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewHexColor(t *testing.T) {
+	cases := []struct {
+		color string
+		hex   string
+		err   bool
+	}{
+		{"#dd22cc", "dd22cc", false},
+		{"#adf", "aaddff", false},
+		{"15d", "1155dd", false},
+		{"a5i", "", true},
+	}
+
+	for _, tc := range cases {
+		hc, err := NewHexColor(tc.color)
+		if tc.err && err == nil {
+			t.Fatalf("expected error for color: %q", tc.color)
+		} else if !tc.err && err != nil {
+			t.Fatalf("error for color %q: %s", tc.color, err)
+		}
+		if assert.NotNil(t, hc) {
+			assert.EqualValues(t, tc.hex, hc.hex)
+		}
+	}
+}