Added MockBackend.rows("col1", "col2")[(...), (...)] helper (#49)

This PR makes testing with `MockBackend` easier.

src/databricks/labs/lsql/backends.py

@@ -301,6 +301,32 @@ def rows_written_for(self, full_name: str, mode: str) -> list[DataclassInstance]
             rows += stub_rows
         return rows
 
+    @staticmethod
+    def rows(*column_names: str):
+        """This method is used to create rows for the mock backend."""
+        number_of_columns = len(column_names)
+        row_factory = Row.factory(list(column_names))
+
+        class MagicFactory:
+            """This class is used to create rows for the mock backend."""
+
+            def __getitem__(self, tuples: list[tuple | list] | tuple[list | tuple]) -> list[Row]:
+                if not isinstance(tuples, (list, tuple)):
+                    raise TypeError(f"Expected list or tuple, got {type(tuples)}")
+                # fix sloppy input
+                if tuples and not isinstance(tuples[0], (list, tuple)):
+                    tuples = [tuples]
+                out = []
+                for record in tuples:
+                    if not isinstance(record, (list, tuple)):
+                        raise TypeError(f"Expected list or tuple, got {type(record)}")
+                    if number_of_columns != len(record):
+                        raise TypeError(f"Expected {number_of_columns} columns, got {len(record)}: {record}")
+                    out.append(row_factory(*record))
+                return out
+
+        return MagicFactory()
+
     @staticmethod
     def _row_factory(klass: Dataclass) -> type:
         return Row.factory([f.name for f in dataclasses.fields(klass)])

src/databricks/labs/lsql/core.py

@@ -66,6 +66,14 @@ def as_dict(self) -> dict[str, Any]:
         """Convert the row to a dictionary with the same conventions as Databricks SDK."""
         return dict(zip(self.__columns__, self, strict=True))
 
+    def __eq__(self, other):
+        """Check if the rows are equal."""
+        if not isinstance(other, Row):
+            return False
+        # compare rows as dictionaries, because the order
+        # of fields in constructor is not guaranteed
+        return self.as_dict() == other.as_dict()
+
     def __contains__(self, item):
         """Check if the column is in the row."""
         return item in self.__columns__

tests/unit/test_backends.py

@@ -346,3 +346,14 @@ def test_mock_backend_save_table():
         Row(first="aaa", second=True),
         Row(first="bbb", second=False),
     ]
+
+
+def test_mock_backend_rows_dsl():
+    rows = MockBackend.rows("foo", "bar")[
+        [1, 2],
+        (3, 4),
+    ]
+    assert rows == [
+        Row(foo=1, bar=2),
+        Row(foo=3, bar=4),
+    ]