feat: configurable snapshot limit, default ten pages

tests/test_snapshot_limit_config.py

@@ -0,0 +1,48 @@
+"""[train] snapshot_limit bounds how many open pull requests one snapshot may list.
+
+The snapshot refuses a listing longer than its limit (SNAPSHOT_LIMIT_EXCEEDED), so a runaway listing never becomes
+a round. The limit was fixed at 300. A repository with more open pull requests than that read no round at all:
+every tick retried, and nothing was admitted or landed, including the configuration change that would have raised
+it. The default is now 1000 (ten 100-row pages), a [train] snapshot_limit overrides it, and every place that builds
+the repository client reads it.
+"""
+
+from __future__ import annotations
+
+import tempfile
+import unittest
+from pathlib import Path
+
+from svrf.app import build
+from svrf.config import ConfigError, from_dict
+
+
+def _config(**train):
+    tmp = Path(tempfile.mkdtemp())
+    doc = {"repo": "o/r", "clone": str(tmp / "clone"), "state_dir": str(tmp / "state"),
+           "gate": {"commands": ["true"]}}
+    if train:
+        doc["train"] = train
+    return from_dict(doc)
+
+
+class SnapshotLimitConfig(unittest.TestCase):
+    def test_the_default_lists_ten_pages(self):
+        self.assertEqual(_config().train.snapshot_limit, 1000)
+
+    def test_a_configured_limit_is_read(self):
+        self.assertEqual(_config(snapshot_limit=2000).train.snapshot_limit, 2000)
+
+    def test_a_limit_that_is_not_a_positive_whole_count_is_refused(self):
+        for bad in (0, -1, 2.5, "1000", True):
+            with self.assertRaises(ConfigError, msg=repr(bad)):
+                _config(snapshot_limit=bad)
+
+    def test_the_daemon_s_repository_client_reads_the_configured_limit(self):
+        daemon = build(_config(snapshot_limit=2000))
+        self.assertEqual(daemon.gh.limit, 2000)
+        self.assertEqual(build(_config()).gh.limit, 1000)
+
+
+if __name__ == "__main__":
+    unittest.main()