Add failing tests

Author: znicholls

tests/unit/test_get_square_root.py

@@ -0,0 +1,27 @@
+"""
+Tests of `example_fgen_basic.get_square_root`
+"""
+
+import pytest
+
+from example_fgen_basic.get_square_root import get_square_root
+from example_fgen_basic.pyfgen_runtime.exceptions import FortranError
+
+
+@pytest.mark.parametrize(
+    "inv, exp, exp_error",
+    (
+        (4.0, 2.0, None),
+        (-4.0, None, pytest.raises(FortranError, match="inv is negative")),
+    ),
+)
+def test_basic(inv, exp, exp_error):
+    if exp is not None:
+        assert get_square_root(inv) == exp
+
+    else:
+        if exp_error is None:
+            raise AssertionError
+
+        with exp_error:
+            get_square_root(inv)