test: strengthen focused unit coverage for core behavior

Cover PR processing, provider helpers, review output rendering,
configuration behavior, retry handling, ticket extraction, code
suggestions, and GitHub app workflows.

These tests target behavior that is important and likely to change,
while keeping production code untouched. They also isolate shared test
state so the new coverage remains order-independent.

This work was developed through multiple rounds of human-led AI
collaboration using codex-cli v0.130.0 with GPT-5.5, GitHub Copilot CLI
v1.0.48 with GPT-5.5, and Claude Opus 4.7.

Author: PeterDaveHello

pr_agent/git_providers/utils.py

@@ -35,7 +35,10 @@ def apply_repo_settings(pr_url):
                 category = 'local'
                 try:
                     fd, repo_settings_file = tempfile.mkstemp(suffix='.toml')
-                    os.write(fd, repo_settings)
+                    try:
+                        os.write(fd, repo_settings)
+                    finally:
+                        os.close(fd)
 
                     try:
                         dynconf_kwargs = {'core_loaders': [],  # DISABLE default loaders, otherwise will load toml files more than once.

tests/unittest/_settings_helpers.py

@@ -0,0 +1,64 @@
+"""Test-only helpers for snapshotting/restoring Dynaconf settings.
+
+Dynaconf's ``settings.unset(key, force=True)`` does not reliably remove a
+dotted leaf (e.g. ``"openai.deployment_id"``) after that leaf was created
+via ``settings.set(...)``. The leaf survives inside the parent section's
+``DynaBox``, which causes state to leak between tests that share the global
+settings singleton.
+
+These helpers provide a SENTINEL-based snapshot so that keys which were
+originally absent are truly removed (not just rewritten to ``None``) during
+restore, including for dotted keys.
+"""
+
+from pr_agent.config_loader import get_settings
+
+SENTINEL = object()
+
+
+def snapshot_settings(keys):
+    """Capture current values for ``keys``; missing keys map to ``SENTINEL``."""
+    settings = get_settings()
+    return {key: settings.get(key, SENTINEL) for key in keys}
+
+
+def _remove_key(settings, key):
+    """Best-effort removal of ``key`` (supports dotted leaves)."""
+    if "." in key:
+        section_name, leaf = key.split(".", 1)
+        container = getattr(settings, section_name, None)
+        if container is None:
+            return
+        # DynaBox lookups are case-insensitive, but ``pop`` requires the
+        # stored casing. Find the matching key and pop it.
+        for stored in list(container.keys()):
+            if stored.lower() == leaf.lower():
+                # ``pop`` with a default never raises KeyError; we narrow to
+                # ``(AttributeError, TypeError)`` to tolerate exotic container
+                # types that don't implement a dict-like ``pop``. Any other
+                # exception is unexpected and should surface so tests fail
+                # loudly rather than mask Dynaconf state leaks.
+                try:
+                    container.pop(stored, None)
+                except (AttributeError, TypeError):
+                    pass
+                return
+        return
+    # ``settings.unset`` raises ``KeyError`` for keys that were never set;
+    # that case is benign for restore. Any other exception (e.g. a Dynaconf
+    # internal error) must propagate so that a broken cleanup is visible
+    # instead of silently leaking state across tests.
+    try:
+        settings.unset(key, force=True)
+    except KeyError:
+        pass
+
+
+def restore_settings(snapshot):
+    """Restore ``snapshot``; truly remove entries whose snapshot is SENTINEL."""
+    settings = get_settings()
+    for key, value in snapshot.items():
+        if value is SENTINEL:
+            _remove_key(settings, key)
+        else:
+            settings.set(key, value)