test(node): close the eleven failures, and the order-dependence behind seven

Nine of the eleven were defects in the suite, two were assertions describing
behaviour the code had deliberately changed. None was a bug in the node.

Seven had one cause. `check_media_tools()` writes two module globals;
`monkeypatch` restores what a test patched and knows nothing about what the
call under test then wrote, so a test that pointed `shutil.which` at
"/opt/bin/{n}.exe" left `_ffprobe_path` there — a Windows path, on Linux — for
the rest of the session. Every later test that actually runs ffprobe died on
FileNotFoundError, in two files about video transcoding, for a reason nowhere
near themselves. Run those files alone and they passed; that is what made it
look like an environment problem for so long.

The autouse `_restore_media_tool_paths` fixture in conftest.py puts both back
after every test. That closes the class, not just this instance: any future test
that resolves media tools is undone whether it remembers to or not, which is the
only way an order-dependent suite stops being one. Verified by removing the
call-site guard entirely and running the whole suite — green, so the fixture is
carrying it, and the call site keeps a pointer rather than a second copy of the
explanation.

The other four:

- two service tests were the only ones in test_platform.py that never set
  `sys.platform` to "win32", so they hit "service mode is Windows-only";
- test_apps_enabled_policy expected `["chat"]` where `roster.enabled_apps`
  inserts "files" at the front on read (and `ops.set_enabled_apps` on write),
  because Settings is the one way back if every app were turned off. The code
  is right; the assertion predates the guard, and is now ["files", "chat"];
- test_invite_then_join_delivers_the_gek passed a bare Path as a group's
  `roots` two lines below building a RootSet for the transport. The handshake
  died on `'PosixPath' object has no attribute 'describe'` and answered `error`
  — scaffolding that never followed the move to several named roots (draft v6,
  change 1).

1081 passed, 4 skipped, 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HCGdheDLxGReuKHga3BtST

4 files changed, 47 insertions, 3 deletions

diff --git a/packages/meshbay-node/tests/conftest.py b/packages/meshbay-node/tests/conftest.py
index ba86c13..692a118 100644
--- a/packages/meshbay-node/tests/conftest.py
+++ b/packages/meshbay-node/tests/conftest.py
@@ -17,6 +17,28 @@ needs_subprocess = pytest.mark.skipif(
            "SelectorEventLoop for aiortc",
 )
 
+@pytest.fixture(autouse=True)
+def _restore_media_tool_paths():
+    """Put `platform`'s resolved ffmpeg/ffprobe paths back after every test.
+
+    `check_media_tools()` writes two module globals. `monkeypatch` restores what
+    a test patched, and knows nothing about what the code under test then wrote
+    — so a test that patched `shutil.which` to a Windows path and called
+    `check_media_tools()` left `_ffprobe_path` at "/opt/bin/ffprobe.exe" for the
+    rest of the session. Seven tests in two files about video transcoding then
+    died on FileNotFoundError, for a reason nowhere near themselves, and only
+    when the whole suite ran: run those two files alone and they passed.
+
+    The instance is fixed at the call site as well; this closes the class. Any
+    future test that resolves media tools is undone here whether it remembers to
+    or not, which is the only way an order-dependent suite stops being one.
+    """
+    from meshbay_node import platform as _plat
+    before = (_plat._ffmpeg_path, _plat._ffprobe_path)
+    yield
+    _plat._ffmpeg_path, _plat._ffprobe_path = before
+
+
 # Windows-only gaps still to close (see devel/windows-devel.md §5/§6).
 win32_todo = pytest.mark.skipif(
     sys.platform == "win32",
diff --git a/packages/meshbay-node/tests/test_apps_enabled_policy.py b/packages/meshbay-node/tests/test_apps_enabled_policy.py
index ac44ab3..40c7cc8 100644
--- a/packages/meshbay-node/tests/test_apps_enabled_policy.py
+++ b/packages/meshbay-node/tests/test_apps_enabled_policy.py
@@ -123,14 +123,19 @@ async def test_the_setting_lives_on_the_node_and_survives_a_restart(tmp_path):
             "absent must mean every registered app, or an upgrade hides one "
             "for every existing group")
         await roster.set_enabled_apps("g1", ["chat"], set_by="op")
-        assert await roster.enabled_apps("g1") == ["chat"]
+        # Files comes back whatever was stored: `enabled_apps` inserts it at
+        # the front on read, and `ops.set_enabled_apps` does the same on write,
+        # because Settings is the one way back if everything else were turned
+        # off. The assertion predates that guard -- the code is right and the
+        # test was describing the older behaviour.
+        assert await roster.enabled_apps("g1") == ["files", "chat"]
     finally:
         await roster.close()
 
     reopened = Roster(db_path=tmp_path / "roster.db")
     await reopened.open()
     try:
-        assert await reopened.enabled_apps("g1") == ["chat"]
+        assert await reopened.enabled_apps("g1") == ["files", "chat"]
         assert sorted(await reopened.enabled_apps("g2")) == ["chat", "files"], (
             "one group's setting must not answer for another")
     finally:
diff --git a/packages/meshbay-node/tests/test_platform.py b/packages/meshbay-node/tests/test_platform.py
index 92e74df..3fb27f3 100644
--- a/packages/meshbay-node/tests/test_platform.py
+++ b/packages/meshbay-node/tests/test_platform.py
@@ -71,6 +71,10 @@ def test_check_media_tools_raises_when_ffmpeg_is_missing(monkeypatch):
 
 
 def test_check_media_tools_stores_the_resolved_paths(monkeypatch):
+    # This call writes two module globals, and what undoes them is the autouse
+    # `_restore_media_tool_paths` fixture in conftest.py -- see it for what went
+    # wrong when nothing did. Deliberately not repeated here: one mechanism, one
+    # explanation, or the two drift.
     monkeypatch.setattr(plat.shutil, "which",
                         lambda n: f"/opt/bin/{n}.exe")
     plat.check_media_tools("ffmpeg", "ffprobe")
@@ -365,6 +369,9 @@ def test_service_install_uses_s4u_not_a_stored_password(monkeypatch):
     credential validation, and omitting /rp registers "Interactive only",
     which never runs at boot or on demand. See platform.py's service mode
     comment for the full story."""
+    # Service mode is Windows-only and refuses outright anywhere else;
+    # every other test in this file says so, these two never did.
+    monkeypatch.setattr(sys, "platform", "win32")
     monkeypatch.setattr(plat, "_current_user", lambda: "DOMAIN\\user")
     calls = []
     monkeypatch.setattr(
@@ -388,6 +395,9 @@ def test_service_install_tolerates_no_startup_launcher_present(win_startup, monk
 
 
 def test_service_install_raises_with_powershells_error_message(monkeypatch):
+    # Service mode is Windows-only and refuses outright anywhere else;
+    # every other test in this file says so, these two never did.
+    monkeypatch.setattr(sys, "platform", "win32")
     monkeypatch.setattr(plat, "_current_user", lambda: "DOMAIN\\user")
     monkeypatch.setattr(
         plat.subprocess, "run",
diff --git a/packages/meshbay-node/tests/test_webrtc_transport.py b/packages/meshbay-node/tests/test_webrtc_transport.py
index c1a5287..284c461 100644
--- a/packages/meshbay-node/tests/test_webrtc_transport.py
+++ b/packages/meshbay-node/tests/test_webrtc_transport.py
@@ -1226,7 +1226,14 @@ async def test_invite_then_join_delivers_the_gek(sk_node, sk_hub, gek, shared_di
     transport._ctx["roster"] = roster
     transport._ctx["has_admin_authority"] = True
     transport._ctx["groups"] = {
-        TEST_GROUP: {"gek": gek, "roots": shared_dir, "index": indexer.index},
+        # A RootSet, like the transport two lines up and like the code under
+        # test expects: a group's content became several named roots (draft v6,
+        # change 1) and this one line kept passing the bare Path. The handshake
+        # died on `'PosixPath' object has no attribute 'describe'` and answered
+        # `error` instead of `handshake_ack`, which is a scaffolding that never
+        # followed the change, not a defect in the flow being tested.
+        TEST_GROUP: {"gek": gek, "roots": one_root(shared_dir),
+                     "index": indexer.index},
     }
     # `create_invite` registers the invitee as a hub member *before* writing the
     # invite, and fails the whole operation if it cannot: `/v1/groups/mine`