[example] add bash usage (#7794)

tests/model/model_utils/test_add_tokens.py

@@ -0,0 +1,46 @@
+# Copyright 2025 the LlamaFactory team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+import pytest
+
+from llamafactory.hparams import ModelArguments
+from llamafactory.model import load_tokenizer
+
+
+TINY_LLAMA3 = os.getenv("TINY_LLAMA3", "llamafactory/tiny-random-Llama-3")
+
+UNUSED_TOKEN = "<|UNUSED_TOKEN|>"
+
+
+@pytest.mark.parametrize("special_tokens", [False, True])
+def test_add_tokens(special_tokens: bool):
+    if special_tokens:
+        model_args = ModelArguments(model_name_or_path=TINY_LLAMA3, add_special_tokens=UNUSED_TOKEN)
+    else:
+        model_args = ModelArguments(model_name_or_path=TINY_LLAMA3, add_tokens=UNUSED_TOKEN)
+
+    tokenizer = load_tokenizer(model_args)["tokenizer"]
+    encoded_ids = tokenizer.encode(UNUSED_TOKEN, add_special_tokens=False)
+    assert len(encoded_ids) == 1
+    decoded_str = tokenizer.decode(encoded_ids, skip_special_tokens=True)
+    if special_tokens:
+        assert decoded_str == ""
+    else:
+        assert decoded_str == UNUSED_TOKEN
+
+
+if __name__ == "__main__":
+    pytest.main([__file__])