feat(training): 实现 DateSplitter 数据划分器

- 新增 DateSplitter 类，支持基于日期范围的一次性训练/测试划分
- 实现日期格式验证和日期范围逻辑检查
- 支持自定义日期列名参数
- 添加完整的单元测试（12个测试用例）
- 在 components 模块导出 DateSplitter

tests/training/test_splitters.py

@@ -0,0 +1,244 @@
+"""测试 DateSplitter 数据划分器
+
+验证一次性日期划分功能。
+"""
+
+import pytest
+import polars as pl
+
+from src.training.components.splitters import DateSplitter
+
+
+class TestDateSplitter:
+    """DateSplitter 测试类"""
+
+    def test_initialization_success(self):
+        """测试正常初始化"""
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        assert splitter.train_start == "20200101"
+        assert splitter.train_end == "20221231"
+        assert splitter.test_start == "20230101"
+        assert splitter.test_end == "20231231"
+
+    def test_invalid_date_format(self):
+        """测试无效的日期格式"""
+        with pytest.raises(ValueError, match="必须是格式为 'YYYYMMDD' 的8位字符串"):
+            DateSplitter(
+                train_start="2020-01-01",  # 错误格式
+                train_end="20221231",
+                test_start="20230101",
+                test_end="20231231",
+            )
+
+    def test_train_start_after_train_end(self):
+        """测试训练集开始日期晚于结束日期"""
+        with pytest.raises(ValueError, match="train_start.*必须早于或等于 train_end"):
+            DateSplitter(
+                train_start="20231231",
+                train_end="20200101",
+                test_start="20230101",
+                test_end="20231231",
+            )
+
+    def test_test_start_after_test_end(self):
+        """测试测试集开始日期晚于结束日期"""
+        with pytest.raises(ValueError, match="test_start.*必须早于或等于 test_end"):
+            DateSplitter(
+                train_start="20200101",
+                train_end="20221231",
+                test_start="20231231",
+                test_end="20230101",
+            )
+
+    def test_overlapping_dates(self):
+        """测试训练集和测试集日期重叠"""
+        with pytest.raises(ValueError, match="必须晚于训练集结束日期"):
+            DateSplitter(
+                train_start="20200101",
+                train_end="20221231",
+                test_start="20220601",  # 在训练集范围内
+                test_end="20231231",
+            )
+
+    def test_split_success(self):
+        """测试正常划分数据"""
+        # 创建测试数据
+        data = pl.DataFrame(
+            {
+                "ts_code": [
+                    "000001.SZ",
+                    "000002.SZ",
+                    "000003.SZ",
+                    "000004.SZ",
+                    "000005.SZ",
+                    "000006.SZ",
+                ],
+                "trade_date": [
+                    "20200101",
+                    "20211231",
+                    "20221231",
+                    "20230101",
+                    "20230601",
+                    "20231231",
+                ],
+                "value": [1.0, 2.0, 3.0, 4.0, 5.0, 6.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        train_data, test_data = splitter.split(data)
+
+        # 验证训练集
+        assert len(train_data) == 3
+        assert train_data["trade_date"].to_list() == [
+            "20200101",
+            "20211231",
+            "20221231",
+        ]
+
+        # 验证测试集
+        assert len(test_data) == 3
+        assert test_data["trade_date"].to_list() == ["20230101", "20230601", "20231231"]
+
+    def test_split_no_matching_train_data(self):
+        """测试训练集无匹配数据"""
+        data = pl.DataFrame(
+            {
+                "ts_code": ["000001.SZ", "000002.SZ"],
+                "trade_date": ["20230101", "20231231"],
+                "value": [1.0, 2.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        train_data, test_data = splitter.split(data)
+
+        # 训练集应该为空
+        assert len(train_data) == 0
+        # 测试集应该有数据
+        assert len(test_data) == 2
+
+    def test_split_no_matching_test_data(self):
+        """测试测试集无匹配数据"""
+        data = pl.DataFrame(
+            {
+                "ts_code": ["000001.SZ", "000002.SZ"],
+                "trade_date": ["20200101", "20211231"],
+                "value": [1.0, 2.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        train_data, test_data = splitter.split(data)
+
+        # 训练集应该有数据
+        assert len(train_data) == 2
+        # 测试集应该为空
+        assert len(test_data) == 0
+
+    def test_split_with_custom_date_col(self):
+        """测试使用自定义日期列名"""
+        data = pl.DataFrame(
+            {
+                "ts_code": ["000001.SZ", "000002.SZ", "000003.SZ"],
+                "date": ["20200101", "20211231", "20230101"],
+                "value": [1.0, 2.0, 3.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        train_data, test_data = splitter.split(data, date_col="date")
+
+        assert len(train_data) == 2
+        assert len(test_data) == 1
+
+    def test_split_missing_date_column(self):
+        """测试数据缺少日期列"""
+        data = pl.DataFrame(
+            {
+                "ts_code": ["000001.SZ"],
+                "value": [1.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        with pytest.raises(ValueError, match="数据中不包含列 'trade_date'"):
+            splitter.split(data)
+
+    def test_repr(self):
+        """测试 __repr__ 方法"""
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20221231",
+            test_start="20230101",
+            test_end="20231231",
+        )
+
+        repr_str = repr(splitter)
+        assert "DateSplitter" in repr_str
+        assert "20200101" in repr_str
+        assert "20221231" in repr_str
+        assert "20230101" in repr_str
+        assert "20231231" in repr_str
+
+    def test_edge_case_same_day_train(self):
+        """测试训练集为单日"""
+        data = pl.DataFrame(
+            {
+                "ts_code": ["000001.SZ"],
+                "trade_date": ["20200101"],
+                "value": [1.0],
+            }
+        )
+
+        splitter = DateSplitter(
+            train_start="20200101",
+            train_end="20200101",
+            test_start="20200102",
+            test_end="20200102",
+        )
+
+        train_data, test_data = splitter.split(data)
+
+        assert len(train_data) == 1
+        assert len(test_data) == 0
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])