fix: default profile picture empty if username contains only one char

backend/internal/model/user.go

@@ -91,10 +91,11 @@ func (u User) FullName() string {
 func (u User) Initials() string {
 	first := utils.GetFirstCharacter(u.FirstName)
 	last := utils.GetFirstCharacter(u.LastName)
-	if first == "" && last == "" && len(u.Username) >= 2 {
-		return strings.ToUpper(u.Username[:2])
+	if first != "" || last != "" {
+		return strings.ToUpper(first + last)
 	}
-	return strings.ToUpper(first + last)
+
+	return strings.ToUpper(utils.GetFirstCharacter(u.Username))
 }
 
 func (u User) LastModified() time.Time {

backend/internal/model/user_test.go

@@ -0,0 +1,52 @@
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUserInitials(t *testing.T) {
+	tests := []struct {
+		name     string
+		user     User
+		expected string
+	}{
+		{
+			name:     "first and last name",
+			user:     User{Username: "username", FirstName: "John", LastName: "Doe"},
+			expected: "JD",
+		},
+		{
+			name:     "first name only",
+			user:     User{Username: "username", FirstName: "John"},
+			expected: "J",
+		},
+		{
+			name:     "last name only",
+			user:     User{Username: "username", LastName: "Doe"},
+			expected: "D",
+		},
+		{
+			name:     "ASCII username",
+			user:     User{Username: "username"},
+			expected: "U",
+		},
+		{
+			name:     "single-character username",
+			user:     User{Username: "a"},
+			expected: "A",
+		},
+		{
+			name:     "empty username",
+			user:     User{},
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, tt.user.Initials())
+		})
+	}
+}