build(tox): includes tox as a test dependency

Author: Karl Wooster

pyproject.toml

@@ -55,6 +55,7 @@ test = [
     "pytest>=8.3.5",
     "pytest-cov>=6.1.1",
     "pytest-sugar>=1.0.0",
+    "tox>=4.25.0",
 ]
 
 [tool.pytest.ini_options]