tests: add basic test

in order to see whether pytest runs.

It in fact does: `uv run pytest`

Signed-off-by: Max R. Carrara <max@aequito.sh>

tests/test_test.py

@@ -0,0 +1,6 @@
+def foo(x):
+    return x + 1
+
+
+def test_answer():
+    assert foo(3) == 4