chore: import upstream snapshot with attribution

tests/python_package_test/test_callback.py

@@ -0,0 +1,65 @@
+# coding: utf-8
+import pytest
+
+import lightgbm as lgb
+
+from .utils import SERIALIZERS, pickle_and_unpickle_object
+
+
+def reset_feature_fraction(boosting_round):
+    return 0.6 if boosting_round < 15 else 0.8
+
+
+@pytest.mark.parametrize("serializer", SERIALIZERS)
+def test_early_stopping_callback_is_picklable(serializer):
+    rounds = 5
+    callback = lgb.early_stopping(stopping_rounds=rounds)
+    callback_from_disk = pickle_and_unpickle_object(obj=callback, serializer=serializer)
+    assert callback_from_disk.order == 30
+    assert callback_from_disk.before_iteration is False
+    assert callback.stopping_rounds == callback_from_disk.stopping_rounds
+    assert callback.stopping_rounds == rounds
+
+
+def test_early_stopping_callback_rejects_invalid_stopping_rounds_with_informative_errors():
+    with pytest.raises(TypeError, match="early_stopping_round should be an integer. Got 'str'"):
+        lgb.early_stopping(stopping_rounds="neverrrr")
+
+
+@pytest.mark.parametrize("stopping_rounds", [-10, -1, 0])
+def test_early_stopping_callback_accepts_non_positive_stopping_rounds(stopping_rounds):
+    cb = lgb.early_stopping(stopping_rounds=stopping_rounds)
+    assert cb.enabled is False
+
+
+@pytest.mark.parametrize("serializer", SERIALIZERS)
+def test_log_evaluation_callback_is_picklable(serializer):
+    periods = 42
+    callback = lgb.log_evaluation(period=periods)
+    callback_from_disk = pickle_and_unpickle_object(obj=callback, serializer=serializer)
+    assert callback_from_disk.order == 10
+    assert callback_from_disk.before_iteration is False
+    assert callback.period == callback_from_disk.period
+    assert callback.period == periods
+
+
+@pytest.mark.parametrize("serializer", SERIALIZERS)
+def test_record_evaluation_callback_is_picklable(serializer):
+    results = {}
+    callback = lgb.record_evaluation(eval_result=results)
+    callback_from_disk = pickle_and_unpickle_object(obj=callback, serializer=serializer)
+    assert callback_from_disk.order == 20
+    assert callback_from_disk.before_iteration is False
+    assert callback.eval_result == callback_from_disk.eval_result
+    assert callback.eval_result is results
+
+
+@pytest.mark.parametrize("serializer", SERIALIZERS)
+def test_reset_parameter_callback_is_picklable(serializer):
+    params = {"bagging_fraction": [0.7] * 5 + [0.6] * 5, "feature_fraction": reset_feature_fraction}
+    callback = lgb.reset_parameter(**params)
+    callback_from_disk = pickle_and_unpickle_object(obj=callback, serializer=serializer)
+    assert callback_from_disk.order == 10
+    assert callback_from_disk.before_iteration is True
+    assert callback.kwargs == callback_from_disk.kwargs
+    assert callback.kwargs == params