add initial tests for compare_asdf

CHANGES.rst

@@ -10,8 +10,8 @@ general
 
 - Fix regression tests for PSF fitting methods [#872]
 
-  - Fix regression test ``compare_asdf`` function replacing use of
-  ``asdf.commands.diff`` with ``deepdiff`` and add ``deepdiff` as
+- Fix regression test ``compare_asdf`` function replacing use of
+  ``asdf.commands.diff`` with ``deepdiff`` and add ``deepdiff`` as
   a test dependency [#868]
 
 ramp_fitting

romancal/regtest/test_regtestdata.py

@@ -0,0 +1,27 @@
+from roman_datamodels import datamodels as rdm
+from roman_datamodels import maker_utils
+
+from romancal.regtest.regtestdata import compare_asdf
+
+
+def test_compare_asdf_identical(tmp_path):
+    fn0 = tmp_path / "test0.asdf"
+    fn1 = tmp_path / "test1.asdf"
+    l2 = rdm.ImageModel(maker_utils.mk_level2_image(shape=(100, 100)))
+    l2.save(fn0)
+    l2.save(fn1)
+    diff = compare_asdf(fn0, fn1)
+    assert diff.identical, diff.report()
+
+
+def test_compare_asdf_differ(tmp_path):
+    fn0 = tmp_path / "test0.asdf"
+    fn1 = tmp_path / "test1.asdf"
+    l2 = rdm.ImageModel(maker_utils.mk_level2_image(shape=(100, 100)))
+    l2.save(fn0)
+    l2.data += 1 * l2.data.unit
+    l2.save(fn1)
+    diff = compare_asdf(fn0, fn1)
+    assert not diff.identical, diff.report()
+    assert "arrays_differ" in diff.diff
+    assert "root['roman']['data']" in diff.diff["arrays_differ"]