# String operations which don't require allocation

try:
    import micropython

    micropython.heap_lock
except (ImportError, AttributeError):
    print("SKIP")
    raise SystemExit

micropython.heap_lock()

# Concatenating empty string returns original string
b"" + b""
b"" + b"1"
b"2" + b""

"" + ""
"" + "1"
"2" + ""

# If no replacements done, returns original string
"foo".replace(",", "_")

micropython.heap_unlock()