Merge pull request #58 from khaeru/feature/assert-units

Add `.testing.assert_units()`

doc/api.rst

@@ -342,3 +342,10 @@ Utilities
 
 .. automodule:: genno.util
    :members:
+
+Utilities for testing
+=====================
+
+.. automodule:: genno.testing
+   :members:
+   :exclude-members: parametrize_quantity_class

doc/whatsnew.rst

@@ -6,8 +6,10 @@ What's new
    :backlinks: none
    :depth: 1
 
-.. Next release
-.. ============
+Next release
+============
+
+- Add :func:`.testing.assert_units` (:pull:`58`).
 
 v1.9.2 (2022-03-03)
 ===================

genno/testing.py

@@ -129,7 +129,7 @@ def add_test_data(c: Computer):
 }
 
 
-def get_test_quantity(key):
+def get_test_quantity(key: Key) -> Quantity:
     """Computation that returns test data."""
     value, unit = _TEST_DATA[key]
     return Quantity(value, name=key.name, units=unit)
@@ -160,10 +160,9 @@ def assert_logs(caplog, message_or_messages=None, at_level=None):
 
     Example
     -------
-
-    def test_foo(caplog):
-        with assert_logs(caplog, 'a message'):
-            logging.getLogger(__name__).info('this is a message!')
+    >>> def test_foo(caplog):
+    ...     with assert_logs(caplog, 'a message'):
+    ...         logging.getLogger(__name__).info('this is a message!')
 
     Parameters
     ----------
@@ -320,6 +319,13 @@ def assert_qty_allclose(
         assert a.attrs == b.attrs
 
 
+def assert_units(qty: Quantity, exp: str) -> None:
+    """Assert that `qty` has units `exp`."""
+    assert (
+        qty.units / qty.units._REGISTRY(exp)
+    ).dimensionless, f"Units '{qty.units:~}'; expected {repr(exp)}"
+
+
 @pytest.fixture(params=["AttrSeries", "SparseDataArray"])
 def parametrize_quantity_class(request):
     """Fixture to run tests twice, for both Quantity implementations."""

genno/tests/test_testing.py

@@ -2,7 +2,13 @@
 
 import pytest
 
-from genno.testing import assert_logs, assert_qty_allclose, assert_qty_equal
+from genno import Quantity
+from genno.testing import (
+    assert_logs,
+    assert_qty_allclose,
+    assert_qty_equal,
+    assert_units,
+)
 
 log = logging.getLogger(__name__)
 
@@ -17,6 +23,10 @@ def test_assert_logs(caplog):
         log.warning("spam and eggs")
 
 
+def test_assert_units():
+    assert_units(Quantity(), "")
+
+
 def test_assert_check_type():
     """Mismatched types in :func:`assert_qty_equal` and :func:`assert_qty_allclose`."""
     with pytest.raises(AssertionError):