def test_9(): assert changeXY("hihi") == "hihi"
def test_7(): assert changeXY("xxx") == "yyy"
def test_8(): assert changeXY("yyhxyi") == "yyhyyi"
def test_5(): assert changeXY("x") == "y"
def test_6(): assert changeXY("") == ""
def test_4(): assert changeXY("h") == "h"
def test_3(): assert changeXY("hiy") == "hiy"
def test_2(): assert changeXY("xhixhix") == "yhiyhiy"
def test_1(): assert changeXY("xxhixx") == "yyhiyy"
def test_0(): assert changeXY("codex") == "codey"