Add unit tests for GenerateRandomString (#5532)

* add unit tests for GenerateRandomString

* remove deprecated call

common/util.go

@@ -360,7 +360,10 @@ func CreateChildContext(
 
 // GenerateRandomString is used for generate test string
 func GenerateRandomString(n int) string {
-	rand.Seed(time.Now().UnixNano())
+	if n <= 0 {
+		return ""
+	}
+
 	letterRunes := []rune("random")
 	b := make([]rune, n)
 	for i := range b {

common/util_test.go

@@ -757,3 +757,16 @@ func TestDomainIDToHistoryShard(t *testing.T) {
 		})
 	}
 }
+
+func TestGenerateRandomString(t *testing.T) {
+	for input, wantSize := range map[int]int{
+		-1: 0,
+		0:  0,
+		10: 10,
+	} {
+		t.Run(fmt.Sprintf("%d", input), func(t *testing.T) {
+			got := GenerateRandomString(input)
+			require.Len(t, got, wantSize)
+		})
+	}
+}