From 143cd70e2feba34c5e9fbf6a6984a88c4aafddec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=A0ar=C5=ABnas=20Nejus?= <snejus@protonmail.com>
Date: Tue, 23 Dec 2025 03:28:12 +0000
Subject: [PATCH] mbcollection: Add tests

---
 beetsplug/mbcollection.py         |   4 +-
 test/plugins/test_mbcollection.py | 149 ++++++++++++++++++++++++++++++
 2 files changed, 151 insertions(+), 2 deletions(-)
 create mode 100644 test/plugins/test_mbcollection.py

diff --git a/beetsplug/mbcollection.py b/beetsplug/mbcollection.py
index 2f9ef709e..376222382 100644
--- a/beetsplug/mbcollection.py
+++ b/beetsplug/mbcollection.py
@@ -101,9 +101,9 @@ class MusicBrainzCollectionPlugin(BeetsPlugin):
 
         offset = 0
         albums_in_collection, release_count = _fetch(offset)
-        for i in range(0, release_count, FETCH_CHUNK_SIZE):
-            albums_in_collection += _fetch(offset)[0]
+        for i in range(FETCH_CHUNK_SIZE, release_count, FETCH_CHUNK_SIZE):
             offset += FETCH_CHUNK_SIZE
+            albums_in_collection += _fetch(offset)[0]
 
         return albums_in_collection
 
diff --git a/test/plugins/test_mbcollection.py b/test/plugins/test_mbcollection.py
new file mode 100644
index 000000000..edf37538d
--- /dev/null
+++ b/test/plugins/test_mbcollection.py
@@ -0,0 +1,149 @@
+import uuid
+from contextlib import nullcontext as does_not_raise
+
+import pytest
+
+from beets.library import Album
+from beets.test.helper import ConfigMixin
+from beets.ui import UserError
+from beetsplug import mbcollection
+
+
+class TestMbCollectionAPI:
+    """Tests for the low-level MusicBrainz API wrapper functions."""
+
+    def test_submit_albums_batches(self, monkeypatch):
+        chunks_received = []
+
+        def mock_add(collection_id, chunk):
+            chunks_received.append(chunk)
+
+        monkeypatch.setattr(
+            "musicbrainzngs.add_releases_to_collection", mock_add
+        )
+
+        # Chunk size is 200. Create 250 IDs.
+        ids = [f"id{i}" for i in range(250)]
+        mbcollection.submit_albums("coll_id", ids)
+
+        # Verify behavioral outcome: 2 batches were sent
+        assert len(chunks_received) == 2
+        assert len(chunks_received[0]) == 200
+        assert len(chunks_received[1]) == 50
+
+
+class TestMbCollectionPlugin(ConfigMixin):
+    """Tests for the MusicBrainzCollectionPlugin class methods."""
+
+    COLLECTION_ID = str(uuid.uuid4())
+
+    @pytest.fixture
+    def plugin(self, monkeypatch):
+        # Prevent actual auth call during init
+        monkeypatch.setattr("musicbrainzngs.auth", lambda *a, **k: None)
+
+        self.config["musicbrainz"]["user"] = "testuser"
+        self.config["musicbrainz"]["pass"] = "testpass"
+
+        plugin = mbcollection.MusicBrainzCollectionPlugin()
+        plugin.config["collection"] = self.COLLECTION_ID
+        return plugin
+
+    @pytest.mark.parametrize(
+        "user_collections,expectation",
+        [
+            (
+                [],
+                pytest.raises(
+                    UserError, match=r"no collections exist for user"
+                ),
+            ),
+            (
+                [{"id": "c1", "entity-type": "event"}],
+                pytest.raises(UserError, match=r"No release collection found."),
+            ),
+            (
+                [{"id": "c1", "entity-type": "release"}],
+                pytest.raises(UserError, match=r"invalid collection ID"),
+            ),
+            (
+                [{"id": COLLECTION_ID, "entity-type": "release"}],
+                does_not_raise(),
+            ),
+        ],
+    )
+    def test_get_collection_validation(
+        self, plugin, monkeypatch, user_collections, expectation
+    ):
+        mock_resp = {"collection-list": user_collections}
+        monkeypatch.setattr("musicbrainzngs.get_collections", lambda: mock_resp)
+
+        with expectation:
+            plugin._get_collection()
+
+    def test_get_albums_in_collection_pagination(self, plugin, monkeypatch):
+        fetched_offsets = []
+
+        def mock_get_releases(collection_id, limit, offset):
+            fetched_offsets.append(offset)
+            count = 150
+            # Return IDs based on offset to verify order/content
+            start = offset
+            end = min(offset + limit, count)
+            return {
+                "collection": {
+                    "release-count": count,
+                    "release-list": [
+                        {"id": f"r{i}"} for i in range(start, end)
+                    ],
+                }
+            }
+
+        monkeypatch.setattr(
+            "musicbrainzngs.get_releases_in_collection", mock_get_releases
+        )
+
+        albums = plugin._get_albums_in_collection("cid")
+        assert len(albums) == 150
+        assert fetched_offsets == [0, 100]
+        assert albums[0] == "r0"
+        assert albums[149] == "r149"
+
+    def test_update_album_list_filtering(self, plugin, monkeypatch):
+        ids_submitted = []
+
+        def mock_submit(_, album_ids):
+            ids_submitted.extend(album_ids)
+
+        monkeypatch.setattr("beetsplug.mbcollection.submit_albums", mock_submit)
+        monkeypatch.setattr(plugin, "_get_collection", lambda: "cid")
+
+        albums = [
+            Album(mb_albumid="invalid-id"),
+            Album(mb_albumid="00000000-0000-0000-0000-000000000001"),
+        ]
+
+        plugin.update_album_list(None, albums)
+        # Behavior: only valid UUID was submitted
+        assert ids_submitted == ["00000000-0000-0000-0000-000000000001"]
+
+    def test_remove_missing(self, plugin, monkeypatch):
+        removed_ids = []
+
+        def mock_remove(_, chunk):
+            removed_ids.extend(chunk)
+
+        monkeypatch.setattr(
+            "musicbrainzngs.remove_releases_from_collection", mock_remove
+        )
+        monkeypatch.setattr(
+            plugin,
+            "_get_albums_in_collection",
+            lambda _: ["r1", "r2", "r3"],
+        )
+
+        lib_albums = [Album(mb_albumid="r1"), Album(mb_albumid="r2")]
+
+        plugin.remove_missing("cid", lib_albums)
+        # Behavior: only 'r3' (missing from library) was removed from collection
+        assert removed_ids == ["r3"]