fix: Fixes and performance improvements in utils package (#331)

backend/internal/utils/string_util_test.go

@@ -0,0 +1,105 @@
+package utils
+
+import (
+	"regexp"
+	"testing"
+)
+
+func TestGenerateRandomAlphanumericString(t *testing.T) {
+	t.Run("valid length returns correct string", func(t *testing.T) {
+		const length = 10
+		str, err := GenerateRandomAlphanumericString(length)
+
+		if err != nil {
+			t.Errorf("Expected no error, got %v", err)
+		}
+		if len(str) != length {
+			t.Errorf("Expected length %d, got %d", length, len(str))
+		}
+
+		matched, err := regexp.MatchString(`^[a-zA-Z0-9]+$`, str)
+		if err != nil {
+			t.Errorf("Regex match failed: %v", err)
+		}
+		if !matched {
+			t.Errorf("String contains non-alphanumeric characters: %s", str)
+		}
+	})
+
+	t.Run("zero length returns error", func(t *testing.T) {
+		_, err := GenerateRandomAlphanumericString(0)
+		if err == nil {
+			t.Error("Expected error for zero length, got nil")
+		}
+	})
+
+	t.Run("negative length returns error", func(t *testing.T) {
+		_, err := GenerateRandomAlphanumericString(-1)
+		if err == nil {
+			t.Error("Expected error for negative length, got nil")
+		}
+	})
+
+	t.Run("generates different strings", func(t *testing.T) {
+		str1, _ := GenerateRandomAlphanumericString(10)
+		str2, _ := GenerateRandomAlphanumericString(10)
+		if str1 == str2 {
+			t.Error("Generated strings should be different")
+		}
+	})
+}
+
+func TestCapitalizeFirstLetter(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{"empty string", "", ""},
+		{"lowercase first letter", "hello", "Hello"},
+		{"already capitalized", "Hello", "Hello"},
+		{"single lowercase letter", "h", "H"},
+		{"single uppercase letter", "H", "H"},
+		{"starts with number", "123abc", "123abc"},
+		{"unicode character", "étoile", "Étoile"},
+		{"special character", "_test", "_test"},
+		{"multi-word", "hello world", "Hello world"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := CapitalizeFirstLetter(tt.input)
+			if result != tt.expected {
+				t.Errorf("CapitalizeFirstLetter(%q) = %q, want %q", tt.input, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestCamelCaseToSnakeCase(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{"empty string", "", ""},
+		{"simple camelCase", "camelCase", "camel_case"},
+		{"PascalCase", "PascalCase", "pascal_case"},
+		{"multipleWordsInCamelCase", "multipleWordsInCamelCase", "multiple_words_in_camel_case"},
+		{"consecutive uppercase", "HTTPRequest", "h_t_t_p_request"},
+		{"single lowercase word", "word", "word"},
+		{"single uppercase word", "WORD", "w_o_r_d"},
+		{"with numbers", "camel123Case", "camel123_case"},
+		{"with numbers in middle", "model2Name", "model2_name"},
+		{"mixed case", "iPhone6sPlus", "i_phone6s_plus"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := CamelCaseToSnakeCase(tt.input)
+			if result != tt.expected {
+				t.Errorf("CamelCaseToSnakeCase(%q) = %q, want %q", tt.input, result, tt.expected)
+			}
+		})
+	}
+}