Improve icolumn.py cc 3/n test_list_column (#413)

Summary:
Pull Request resolved: #413

Pull Request resolved: #408

Improves test coverage for icolumn.py through test_list_column.

Reviewed By: wenleix

Differential Revision: D37492647

fbshipit-source-id: 7674aeac36d94a07fad0147d1d2f79a2ede3f905

Author: andrewaikens87

torcharrow/icolumn.py

@@ -254,8 +254,8 @@ def cast(self, dtype):
                         res._append_value(fun(i))
                 return res._finalize()
             else:
-                raise TypeError('f"{astype}({dtype}) is not supported")')
-        raise TypeError('f"{astype} for {type(self).__name__} is not supported")')
+                raise TypeError(f"{dtype} for {type(self).__name__} is not supported")
+        raise TypeError(f"{self.dtype} for {type(self).__name__} is not supported")
 
     # public simple observers -------------------------------------------------
 

torcharrow/test/test_list_column.py

@@ -208,6 +208,23 @@ def base_test_fixed_size_list(self):
             f"Unexpected failure reason: {str(ex.exception)}",
         )
 
+    def base_test_cast(self):
+        list_dtype = dt.List(item_dtype=dt.int64, fixed_size=2)
+        c_list = ta.column(
+            [[1, 2], [3, 4]],
+            dtype=list_dtype,
+            device=self.device,
+        )
+
+        int_dtype = dt.int64
+        # TODO: Nested cast should be supported in the future
+        for arg in (int_dtype, list_dtype):
+            with self.assertRaisesRegexp(
+                expected_exception=TypeError,
+                expected_regex=r"List\(int64, fixed_size=2\) for.*is not supported",
+            ):
+                c_list.cast(arg)
+
 
 if __name__ == "__main__":
     unittest.main()

torcharrow/test/test_list_column_cpu.py

@@ -46,6 +46,9 @@ def test_map_reduce_etc(self):
     def test_fixed_size_list(self):
         self.base_test_fixed_size_list()
 
+    def test_cast(self):
+        self.base_test_cast()
+
 
 if __name__ == "__main__":
     unittest.main()