add test for slice

pkg/util/slice/slice_test.go

@@ -89,3 +89,20 @@ func TestShuffleStrings(t *testing.T) {
 		}
 	}
 }
+
+func TestContainsString(t *testing.T) {
+	src := []string{"aa", "bb", "cc"}
+	if !ContainsString(src, "bb", nil) {
+		t.Errorf("ContainsString didn't find the string as expected")
+	}
+
+	modifier := func(s string) string {
+		if s == "cc" {
+			return "ee"
+		}
+		return s
+	}
+	if !ContainsString(src, "ee", modifier) {
+		t.Errorf("ContainsString didn't find the string by modifier")
+	}
+}