def METHOD_NAME(self):
    tokenizer = GPTTokenizer.from_pretrained(self.tmpdirname, pad_token="<pad>")
    # Simple input
    s = "This is a simple input"
    s2 = ["This is a simple input looooooooong", "This is a simple input"]
    p = ("This is a simple input", "This is a pair")
    p2 = [
        ("This is a simple input loooooong", "This is a simple input"),
        ("This is a simple pair loooooong", "This is a simple pair"),
    ]
    pad_token_id = tokenizer.pad_token_id
    out_s = tokenizer(s, padding="max_length", max_length=30, return_tensors="np", return_attention_mask=True)
    out_s2 = tokenizer(s2, padding=True, truncate=True, return_tensors="np", return_attention_mask=True)
    out_p = tokenizer(*p, padding="max_length", max_length=60, return_tensors="np", return_attention_mask=True)
    out_p2 = tokenizer(p2, padding=True, truncate=True, return_tensors="np", return_attention_mask=True)
    # s
    # test single string max_length padding
    self.assertEqual(out_s["input_ids"].shape[-1], 30)
    self.assertTrue(pad_token_id in out_s["input_ids"])
    self.assertTrue(0 in out_s["attention_mask"])
    # s2
    # test automatic padding
    self.assertEqual(out_s2["input_ids"].shape[-1], 33)
    # long slice doesn't have padding
    self.assertFalse(pad_token_id in out_s2["input_ids"][0])
    self.assertFalse(0 in out_s2["attention_mask"][0])
    # short slice does have padding
    self.assertTrue(pad_token_id in out_s2["input_ids"][1])
    self.assertTrue(0 in out_s2["attention_mask"][1])
    # p
    # test single pair max_length padding
    self.assertEqual(out_p["input_ids"].shape[-1], 60)
    self.assertTrue(pad_token_id in out_p["input_ids"])
    self.assertTrue(0 in out_p["attention_mask"])
    # p2
    # test automatic padding pair
    self.assertEqual(out_p2["input_ids"].shape[-1], 52)
    # long slice pair doesn't have padding
    self.assertFalse(pad_token_id in out_p2["input_ids"][0])
    self.assertFalse(0 in out_p2["attention_mask"][0])
    # short slice pair does have padding
    self.assertTrue(pad_token_id in out_p2["input_ids"][1])
    self.assertTrue(0 in out_p2["attention_mask"][1])