[v1] support read dataset (#9243)

tests_v1/core/test_data_engine.py

@@ -0,0 +1,40 @@
+# 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 random
+
+import pytest
+from datasets import load_dataset
+
+from llamafactory.v1.config.data_args import DataArguments
+from llamafactory.v1.core.data_engine import DataEngine
+
+
+TINY_DATA = os.getenv("TINY_DATA", "llamafactory/v1-sft-demo")
+
+
+@pytest.mark.parametrize("num_samples", [16])
+def test_map_dataset(num_samples: int):
+    data_args = DataArguments(dataset=TINY_DATA)
+    data_engine = DataEngine(data_args)
+    original_data = load_dataset(TINY_DATA, split="train")
+    indexes = random.choices(range(len(data_engine)), k=num_samples)
+    for index in indexes:
+        print(data_engine[index])
+        assert data_engine[index] == original_data[index]
+
+
+if __name__ == "__main__":
+    test_map_dataset(1)