test: add tests for discover() functionality

8 tests covering:
- Basic discovery returns entries
- Count limits
- Topic filtering (case-insensitive)
- Empty archive handling
- Vitality boost via touch

nexus/mnemosyne/tests/test_discover.py

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+"""Tests for Mnemosyne discover functionality."""
+
+import tempfile
+from pathlib import Path
+
+from nexus.mnemosyne.archive import MnemosyneArchive
+from nexus.mnemosyne.ingest import ingest_event
+
+
+def _make_archive_with_entries():
+    """Helper: create an archive with test entries."""
+    path = Path(tempfile.mkdtemp()) / "test_archive.json"
+    archive = MnemosyneArchive(archive_path=path, auto_embed=False)
+    ingest_event(archive, title="Python automation", content="Building tools in Python", topics=["python", "automation"])
+    ingest_event(archive, title="Cooking pasta", content="How to make carbonara", topics=["cooking"])
+    ingest_event(archive, title="Bitcoin basics", content="Understanding Bitcoin and blockchain", topics=["bitcoin", "crypto"])
+    ingest_event(archive, title="AI agents", content="Building autonomous AI agents", topics=["ai", "agents"])
+    ingest_event(archive, title="Meditation guide", content="Mindfulness and meditation techniques", topics=["wellness"])
+    return archive
+
+
+def test_discover_returns_entries():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=3)
+    assert len(results) == 3
+    for r in results:
+        assert "entry_id" in r
+        assert "title" in r
+        assert "content_preview" in r
+        assert "topics" in r
+        assert "vitality" in r
+        assert "age_days" in r
+
+
+def test_discover_respects_count():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=2)
+    assert len(results) == 2
+
+
+def test_discover_count_exceeds_entries():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=100)
+    assert len(results) == archive.count
+
+
+def test_discover_topic_filter():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=10, topic="python")
+    assert len(results) == 1
+    assert results[0]["title"] == "Python automation"
+
+
+def test_discover_topic_case_insensitive():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=10, topic="Python")
+    assert len(results) == 1
+
+
+def test_discover_empty_topic_returns_nothing():
+    archive = _make_archive_with_entries()
+    results = archive.discover(count=10, topic="nonexistent")
+    assert len(results) == 0
+
+
+def test_discover_boosts_vitality():
+    archive = _make_archive_with_entries()
+    # Get initial vitality
+    before = archive.fading(limit=5)
+    # Discover (which touches entries)
+    archive.discover(count=3)
+    # The touched entries should have higher vitality now
+    after = archive.fading(limit=5)
+    # At least some entries should have changed vitality
+    before_vitals = {e["entry_id"]: e["vitality"] for e in before}
+    after_vitals = {e["entry_id"]: e["vitality"] for e in after}
+    changed = sum(1 for eid in before_vitals if eid in after_vitals and abs(before_vitals[eid] - after_vitals[eid]) > 0.001)
+    assert changed >= 1, "Discover should touch and boost vitality of selected entries"
+
+
+def test_discover_empty_archive():
+    path = Path(tempfile.mkdtemp()) / "empty.json"
+    archive = MnemosyneArchive(archive_path=path, auto_embed=False)
+    results = archive.discover(count=5)
+    assert len(results) == 0