Add unit test

ludwig/data/dataframe/daft.py

@@ -64,7 +64,7 @@ class LudwigDaftSeries:
     ```
     """
 
-    def __init__(self, expr: daft.Expression):
+    def __init__(self, expr: daft.expressions.Expression):
         self._expr = expr
 
     @property

tests/ludwig/data/dataframe/test_daft.py

@@ -0,0 +1,32 @@
+import daft
+import numpy as np
+import pytest
+
+from ludwig.data.dataframe.daft import DaftEngine, LudwigDaftDataframe, LudwigDaftSeries
+
+
+@pytest.fixture(scope="function")
+def df() -> LudwigDaftDataframe:
+    data = {
+        "a": [i for i in range(10)],
+        "b": ["a" * i for i in range(10)],
+        "c": [np.zeros((i, i)) for i in range(1, 11)],
+    }
+    return LudwigDaftDataframe(daft.from_pydict(data))
+
+
+@pytest.fixture(scope="function", params=[1, 2])
+def engine(request) -> DaftEngine:
+    parallelism = request.param
+    return DaftEngine(parallelism=parallelism)
+
+
+def test_df_like(df: LudwigDaftDataframe, engine: DaftEngine):
+    s1 = LudwigDaftSeries(df["a"].expr * 2)
+    s2 = LudwigDaftSeries(df["b"].expr + "_suffix")
+    df = engine.df_like(df, {"foo": s1, "bar": s2})
+    pd_df = engine.compute(df)
+
+    assert list(pd_df.columns) == ["a", "b", "c", "foo", "bar"]
+    np.testing.assert_equal(np.array(pd_df["foo"]), np.array(pd_df["a"] * 2))
+    np.testing.assert_equal(np.array(pd_df["bar"]), np.array([item + "_suffix" for item in pd_df["b"]]))