diff --git a/pkg/utils/utils_test.go b/pkg/utils/utils_test.go
index 3bb61ad..589e281 100644
--- a/pkg/utils/utils_test.go
+++ b/pkg/utils/utils_test.go
@@ -22,6 +22,7 @@ import (
 // - ConvertMultiByteCharToIteratingRule()
 // - SplitBySeparatorString()
 // - ReplaceSubstring()
+// - SubstringMap()
 //
 // ** Validation Functions **
 // - CheckASCIIString()
@@ -400,6 +401,38 @@ func TestReplaceSubstring(t *testing.T) {
 	}
 }
 
+// Unit Test for SubstringMap()
+func TestSubstringMap(t *testing.T) {
+
+	// Define a test case struct
+	type TestCase struct {
+		input  map[string]int
+		start  int
+		end    int
+		output map[string]int
+	}
+
+	// Define test cases
+	testCases := []TestCase{
+		{map[string]int{"love1": 1, "love2": 1, "love3": 1}, 0, 4, map[string]int{"love": 3}},
+		{map[string]int{"<31": 1, "<32": 1, "<33": 1}, 1, 2, map[string]int{"3": 3}},
+		{map[string]int{"爱1": 1, "爱2": 1, "爱3": 1}, 0, 3, map[string]int{"爱": 3}},
+	}
+
+	// Run test cases
+	for _, testCase := range testCases {
+		input := testCase.input
+		start := testCase.start
+		end := testCase.end
+		output := testCase.output
+
+		given := SubstringMap(input, start, end, false, false)
+		if CheckAreMapsEqual(given, output) == false {
+			t.Errorf("SubstringMap(%v, %v, %v) = %v; want %v", input, start, end, given, output)
+		}
+	}
+}
+
 // Unit Test for CheckASCIIString()
 func TestCheckASCIIString(t *testing.T) {