TST: assert_extension_array_equal is inconsistent in how precision is handled

[jschendel]

Code Sample, a copy-pastable example if possible

Setup:

In [2]: values1 = np.array([-0.17387645482451206, 0.3414148016424936])
   ...: values2 = np.array([-0.17387645482451206, 0.3414148016424937])

In [3]: df1 = pd.DataFrame({'a': values1, 'b': ['foo', 'bar']})
   ...: df2 = pd.DataFrame({'a': values2, 'b': ['foo', 'bar']})

By default, assert_frame_equal will not fail on a difference in precision that's as slight as what's above, and will only detect the difference if check_exact=True is passed:

In [4]: tm.assert_frame_equal(df1, df2)

In [5]: tm.assert_frame_equal(df1, df2, check_exact=True)
---------------------------------------------------------------------------
AssertionError: DataFrame.iloc[:, 0] are different

DataFrame.iloc[:, 0] values are different (50.0 %)
[left]:  [-0.173876454825, 0.341414801642]
[right]: [-0.173876454825, 0.341414801642]

However, when extension arrays are introduced, which causes assert_frame_equal to dispatch to assert_extension_array_equal, this difference in precision is detected by default:

In [6]: tm.assert_frame_equal(df1.to_sparse(), df2.to_sparse())
---------------------------------------------------------------------------
AssertionError: numpy array are different

numpy array values are different (50.0 %)
[left]:  [-0.17387645482451206, 0.3414148016424936]
[right]: [-0.17387645482451206, 0.3414148016424937]

Proposed Solution

Looking at the source code for assert_extension_array_equal, it does not accept any of the keyword arguments that the assert_*_equal functions take in regards to precision:

pandas/pandas/util/testing.py

Lines 1192 to 1198 in e413c49

	def assert_extension_array_equal(left, right):
	"""Check that left and right ExtensionArrays are equal.
	Parameters
	----------
	left, right : ExtensionArray
	The two arrays to compare

I'd like to add check_exact, check_less_precise, and check_dtype parameters to assert_extension_array_equal with the same defaults as the other assert_*_equal functions.

Note that this would resolve #23605, which is the source of my example.

cc @TomAugspurger : Thoughts on this? Is there a reason we'd want check_exact style checking by default?

[TomAugspurger]

This all sounds good. I think we would want to match the defaults for the rest of the asserts.

[jreback]

yep this sounds good