Move tests to tests folder

INSTALL.txt

@@ -15,14 +15,7 @@ or, if additional access rights are needed (Unix):
 
   sudo python setup.py install
 
-* The tests programs (test_*.py) are meant to be run through the Nose
-testing framework.  This can be achieved for instance with a command
+* The tests programs (test_*.py) are meant to be run through pytest.  This can be achieved for instance with a command
 like
 
-  nosetests -sv uncertainties/
-
-or simply
-
-  nosetests uncertainties/
-
-(for a less verbose output).
+  pytest ./tests

pyproject.toml

@@ -57,3 +57,6 @@ Changelog = "https://github.com/lmfit/uncertainties/blob/master/CHANGES.rst"
 
 [project.optional-dependencies]
 optional = ["numpy"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]