diff --git a/04_largest_palindrome_product/main.go b/04_largest_palindrome_product/main.go
index 2491f3d..8d26c5a 100644
--- a/04_largest_palindrome_product/main.go
+++ b/04_largest_palindrome_product/main.go
@@ -7,11 +7,15 @@ import (
 )
 
 func main() {
+	findMaxPalindrome(100, 999)
+}
+
+func findMaxPalindrome(start, end int) int {
 	var n int
 	var x int
 	var y int
-	for i := 100; i < 1000; i++ {
-		for j := 100; j < 1000; j++ {
+	for i := start; i < end+1; i++ {
+		for j := start; j < end+1; j++ {
 			tmp := i * j
 			if tmp > n && IsPalindrome(tmp) {
 				x = i
@@ -21,6 +25,7 @@ func main() {
 		}
 	}
 	fmt.Println(x, y, n)
+	return n
 }
 
 func IsPalindrome(n int) bool {
diff --git a/04_largest_palindrome_product/palindrome_test.go b/04_largest_palindrome_product/palindrome_test.go
index e276089..74d231e 100644
--- a/04_largest_palindrome_product/palindrome_test.go
+++ b/04_largest_palindrome_product/palindrome_test.go
@@ -46,3 +46,28 @@ func TestIsPalindrome(t *testing.T) {
 		})
 	}
 }
+
+func Test_findMaxPalindrome(t *testing.T) {
+	type args struct {
+		start int
+		end   int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{
+			"1",
+			args{10, 99},
+			9009,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := findMaxPalindrome(tt.args.start, tt.args.end); got != tt.want {
+				t.Errorf("findMaxPalindrome() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}