def test_read_instances_empty_fields(self):
@dataclass(frozen=True)
class Dc:
pass
t = TypedDfBuilder("T").reserve("animal", dtype=str).build()
df = t.from_dataclass_instances([Dc()])
assert len(df) == 1
assert "animal" not in df.columns
def test_read_instances(self):
@dataclass(frozen=True)
class Dc:
animal: str
val: Optional[int]
t = TypedDfBuilder("T").require("animal", dtype=str).reserve("age", dtype=int).build()
df = t.from_dataclass_instances([Dc("cat", 1), Dc("kitten", 2)])
assert len(df) == 2
assert df.to_numpy().tolist() == [["cat", 1], ["kitten", 2]]
def test_read_instances_empty(self):
t = TypedDfBuilder("T").require("animal", dtype=str).build()
df = t.from_dataclass_instances([])
assert len(df) == 0
