Add some test and prelimary code

.vscode/settings.json

@@ -14,9 +14,13 @@
         "pkgs/sagemath-objects/sage": true,
         "pkgs/sagemath-standard/sage": true,
     },
+    "python.testing.pytestPath": "./sage -t",
     "python.testing.pytestEnabled": true,
     "python.testing.pytestArgs": [
-        "src"
+        "src/test_doctests.py",
+        "--rootdir=src/sage",
+        "-c=src/tox.ini",
+        "--doctest-modules",
     ],
     "python.testing.unittestEnabled": false,
 }

src/test_doctest.py

@@ -0,0 +1,11 @@
+def something():
+    """ a doctest in a docstring
+    >>> something()
+    42
+
+    some other doctest
+
+    >>> something() + 1
+    43
+    """
+    return 42

src/tox.ini

@@ -155,6 +155,7 @@ commands = codespell \
 
 [pytest]
 python_files = *_test.py
+norecursedirs = local prefix venv build pkgs .git src/sage/pkgs src/doc src/bin src/sage/src/sage_setup
 
 [coverage:run]
 source = sage