diff --git a/fastlyExp.go b/fastlyExp.go
deleted file mode 100644
index 19a99e7..0000000
--- a/fastlyExp.go
+++ /dev/null
@@ -1,22 +0,0 @@
-package main
-
-import (
-	"encoding/base64"
-	"encoding/binary"
-	"encoding/hex"
-	"fmt"
-	"os"
-	"strings"
-	"time"
-)
-
-func main() {
-	if len(os.Args) > 1 {
-		decoded, _ := base64.StdEncoding.DecodeString(strings.Replace(os.Args[1], "%3D", "=", -1))
-		token := string(decoded)
-		byteTime, _ := hex.DecodeString(token[:strings.Index(token, "_")])
-		fmt.Println("Token expires:", time.Unix(int64(binary.BigEndian.Uint32(byteTime)), 0))
-	} else {
-		fmt.Println("Missing token.")
-	}
-}
diff --git a/fastly_exp.go b/fastly_exp.go
new file mode 100644
index 0000000..8b1beb3
--- /dev/null
+++ b/fastly_exp.go
@@ -0,0 +1,39 @@
+package main
+
+import (
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+)
+
+func main() {
+	if len(os.Args) > 1 {
+		token, err := decode(os.Args[1])
+		if err != nil {
+			fmt.Printf("Error: %s", err.Error())
+		}
+		fmt.Printf("Token expires: %s", token)
+	} else {
+		fmt.Println("Missing token.")
+	}
+}
+
+// decode a Fastly Token. Returns expiration or error.
+func decode(token string) (string, error) {
+	decoded, err := base64.StdEncoding.DecodeString(strings.Replace(token, "%3D", "=", -1))
+	if err != nil {
+		return "", err
+	}
+
+	decToken := string(decoded)
+	byteTime, err := hex.DecodeString(decToken[:strings.Index(decToken, "_")])
+	if err != nil {
+		return "", err
+	}
+
+	return time.Unix(int64(binary.BigEndian.Uint32(byteTime)), 0).UTC().String(), nil
+}
diff --git a/fastly_exp_test.go b/fastly_exp_test.go
new file mode 100644
index 0000000..658d65e
--- /dev/null
+++ b/fastly_exp_test.go
@@ -0,0 +1,52 @@
+package main
+
+import "testing"
+
+func Test_decode(t *testing.T) {
+	type args struct {
+		token string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    string
+		wantErr bool
+	}{
+		{
+			"success",
+			args{
+				"NWZmY2U4MWFfY2ViMDViZWRkOWYwZTRkY2NkYTIxOWE3NjRhYmNlMjczZWViMWNmYWQ2ZTc4OTQzYmViNTE0YWMwZjBlMjFjNQ%3D%3D",
+			},
+			"2021-01-12 00:06:50 +0000 UTC",
+			false,
+		},
+		{
+			"error (not base64)",
+			args{
+				"NWZmY2U4MWFfY2ViM",
+			},
+			"",
+			true,
+		},
+		{
+			"error (not hex)",
+			args{
+				"aGVsbG9fdGhlcmU=",
+			},
+			"",
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := decode(tt.args.token)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("decode() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("decode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}