added tests for existing invariants

Makefile

@@ -6,8 +6,10 @@
 # the `testcov` target can be used to build a local copy of the code coverage in HTML
 #   $ make testcov
 
-TESTPATH="tests"
-PYTESTOPTS="-v"
+PYTEST        = pytest
+TESTPATH      = tests
+PYTESTOPTS    = -v
+COVERAGE      = coverage
 
 release:
 	rm dist/* || :
@@ -17,7 +19,10 @@ release:
 	hub release create -a dist/*.tar.gz -a dist/*.whl -m 'v$(VERSION)' $(VERSION)
 
 test:
-	pytest $(TESTPATH) $(PYTESTOPTS)
+	$(PYTEST) $(TESTPATH) $(PYTESTOPTS)
 
 testcov:
-	coverage run --source=. -m pytest $(TESTPATH) $(PYTESTOPTS) && coverage html
+	$(COVERAGE) run --source=pybryt -m pytest $(TESTPATH) $(PYTESTOPTS) 
+
+covhtml: testcov
+	$(COVERAGE) html

tests/annotations/test_invariants.py

@@ -0,0 +1,23 @@
+"""Tests for value annotation invariants"""
+
+import numpy as np
+
+from unittest import mock
+
+from pybryt.annotations.invariants import *
+
+
+def test_call_structure():
+    with mock.patch.object(invariant, "run") as mocked_run:
+        invariant()
+        mocked_run.assert_called()
+
+    assert invariant([]) is None
+
+
+def test_string_capitalization():
+    np.random.seed(42)
+    values = ["someString", "some_otherO!I(I*$NDdnnfkf", 120484, ["hi", "there"], np.random.uniform(size=100)]
+    expected_values = [s.lower() if isinstance(s, str) else s for s in values]
+    np.testing.assert_equal(string_capitalization(values), expected_values)
+