Add status string for unknown status codes

status.go

@@ -1,5 +1,7 @@
 package ftp
 
+import "fmt"
+
 // FTP status codes, defined in RFC 959
 const (
 	StatusInitiating    = 100
@@ -109,5 +111,9 @@ var statusText = map[int]string{
 
 // StatusText returns a text for the FTP status code. It returns the empty string if the code is unknown.
 func StatusText(code int) string {
-	return statusText[code]
+	str, ok := statusText[code]
+	if !ok {
+		str = fmt.Sprintf("Unknown status code: %d", code)
+	}
+	return str
 }

status_test.go

@@ -1,17 +1,12 @@
 package ftp
 
-import "testing"
+import (
+	"testing"
 
-func TestValidStatusText(t *testing.T) {
-	txt := StatusText(StatusInvalidCredentials)
-	if txt == "" {
-		t.Fatal("exptected status text, got empty string")
-	}
-}
+	"github.com/stretchr/testify/assert"
+)
 
-func TestInvalidStatusText(t *testing.T) {
-	txt := StatusText(0)
-	if txt != "" {
-		t.Fatalf("got status text %q, expected empty string", txt)
-	}
+func TestStatusText(t *testing.T) {
+	assert.Equal(t, "Unknown status code: 0", StatusText(0))
+	assert.Equal(t, "Invalid username or password.", StatusText(StatusInvalidCredentials))
 }