Created some simple tests of teh description to get started.

tests/test_supercell_step.py

@@ -5,3 +5,59 @@
 
 import pytest  # noqa: F401
 import supercell_step  # noqa: F401
+import re
+
+
+@pytest.fixture
+def instance():
+    instance = supercell_step.Supercell()
+    instance._id = (1,)
+    return instance
+
+
+def test_construction():
+    """Simplest test that we can make a SUPERCELL object"""
+    instance = supercell_step.Supercell()
+    assert (
+        str(type(instance)) == "<class 'supercell_step.supercell.Supercell'>"
+    )
+
+
+def test_version():
+    """Test that the object returns a version"""
+    instance = supercell_step.Supercell()
+    result = instance.version
+    assert isinstance(result, str) and len(result) > 0
+
+
+def test_git_revision():
+    """Test that the object returns a git revision"""
+    instance = supercell_step.Supercell()
+    result = instance.git_revision
+    assert isinstance(result, str) and len(result) > 0
+
+
+def test_description_text_default(instance):
+    """Test the default description text"""
+
+    assert re.fullmatch(
+        (
+            r'Step 1: Supercell  [-+.0-9a-z]+\n'
+            r'    Create a 2 x 2 x 2 supercell from the current cell'
+        ), instance.description_text()
+    ) is not None
+
+
+def test_description_text_expr_expr(instance):
+    """Test the default description text"""
+
+    assert re.fullmatch(
+        (
+            r'Step 1: Supercell  [-+.0-9a-z]+\n'
+            r'    Create a 5 x 4 x 3 supercell from the current cell'
+        ), instance.description_text({
+            'na': 5,
+            'nb': 4,
+            'nc': 3,
+        })
+    ) is not None