tests: add tests for installed UV

Signed-off-by: Henry Schreiner <[email protected]>

nox/sessions.py

@@ -21,8 +21,8 @@
 import os
 import pathlib
 import re
-import subprocess
 import shutil
+import subprocess
 import sys
 import unicodedata
 from collections.abc import (
@@ -562,7 +562,7 @@ def _run(
             self.virtualenv.venv_backend == "uv"
             and args[0] == "uv"
             and nox.virtualenv.UV != "uv"
-            and shutil.which("uv", path=self.bin) is None
+            and shutil.which("uv", path=self.bin) is None  # Session uv takes priority
         ):
             args = (nox.virtualenv.UV, *args[1:])
 

tests/test_sessions.py

@@ -895,7 +895,7 @@ class SessionNoSlots(nox.sessions.Session):
         session = SessionNoSlots(runner=runner)
 
         monkeypatch.setattr(nox.virtualenv, "UV", "/some/uv")
-        monkeypatch.setattr(shutil, "which", lambda x: None)
+        monkeypatch.setattr(shutil, "which", lambda x, path=None: None)
 
         with mock.patch.object(nox.command, "run", autospec=True) as run:
             session.install("requests", "urllib3", silent=False)
@@ -910,6 +910,24 @@ class SessionNoSlots(nox.sessions.Session):
                 "urllib3",
             )
 
+        # user installs uv in the session venv
+        monkeypatch.setattr(
+            shutil, "which", lambda x, path="": path + "/uv" if x == "uv" else None
+        )
+
+        with mock.patch.object(nox.command, "run", autospec=True) as run:
+            session.install("requests", "urllib3", silent=False)
+            run.assert_called_once()
+
+            ((call_args,), _) = run.call_args
+            assert call_args == (
+                "uv",
+                "pip",
+                "install",
+                "requests",
+                "urllib3",
+            )
+
     def test___slots__(self):
         session, _ = self.make_session_and_runner()
         with pytest.raises(AttributeError):