Fix dependency-group name normalization

Author: robsdedude

docs/changelog/3539.bugfix.rst

@@ -0,0 +1 @@
+Fix dependency-group name normalization.

tests/tox_env/python/test_python_runner.py

@@ -334,14 +334,14 @@ def test_dependency_groups_not_list(tox_project: ToxProjectCreator) -> None:
             """,
             "pyproject.toml": """
             [dependency-groups]
-            test = 1
+            teSt = 1
             """,
         },
     )
     result = project.run("r", "-e", "py")
 
     result.assert_failed()
-    assert "py: failed with dependency group 'test' is not a list\n" in result.out
+    assert "py: failed with dependency group 'teSt' is not a list\n" in result.out
 
 
 def test_dependency_groups_bad_requirement(tox_project: ToxProjectCreator) -> None:
@@ -398,12 +398,12 @@ def test_dependency_groups_cyclic(tox_project: ToxProjectCreator) -> None:
             """,
             "pyproject.toml": """
             [dependency-groups]
-            test = [ { include-group = "type" } ]
-            type = [ { include-group = "test" } ]
+            teSt = [ { include-group = "type" } ]
+            tyPe = [ { include-group = "test" } ]
             """,
         },
     )
     result = project.run("r", "-e", "py")
 
     result.assert_failed()
-    assert "py: failed with Cyclic dependency group include: 'test' -> ('test', 'type')\n" in result.out
+    assert "py: failed with Cyclic dependency group include: 'teSt' -> ('teSt', 'tyPe')\n" in result.out