docs: add test refactor implementation plan

1 month ago · ebb663aa8f
parent 07a89a207c
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--- a/thoughts/shared/plans/2026-03-23-test-refactor-no-mocks.md
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@ -0,0 +1,723 @@
+# Test Refactor: No Mocks Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Replace sys.modules injection, monkeypatching, and exception-swallowing in the 4 new test files with tests that run real production code against in-memory DuckDB and injected fake callables.
+
+**Architecture:** Add optional `db` and `embedder` parameters to three pipeline functions (backwards-compatible defaults). Add `mem_db` and `fake_embedder` pytest fixtures to `tests/conftest.py`. Rewrite four test files to use these fixtures with no monkeypatching.
+
+**Tech Stack:** Python, pytest, duckdb (`:memory:`), existing `MotionDatabase` class
+
+---
+
+## File Map
+
+| File | Action | What changes |
+|------|--------|-------------|
+| `pipeline/ai_provider_wrapper.py` | Modify | Add `db=None` and `embedder=None` params to `get_embeddings_with_retry` |
+| `pipeline/text_pipeline.py` | Modify | Add `db=None` override to `ensure_text_embeddings` and `ensure_text_embeddings_for_ids`; pass it into `ai_wrapper.get_embeddings_with_retry` |
+| `similarity/compute.py` | Modify | Add `db=None` override param to `compute_similarities` |
+| `tests/conftest.py` | Modify | Add `mem_db` and `fake_embedder` fixtures |
+| `tests/test_database_audit.py` | Rewrite | Use `mem_db`; assert event in DB table, not on disk |
+| `tests/test_ai_provider_wrapper.py` | Rewrite | Use `mem_db` + `fake_embedder`; test retry and audit event |
+| `tests/test_rerun_embeddings_retry.py` | Rewrite | Remove sys.modules hack; use real pipeline with `fake_embedder` |
+| `tests/test_similarity_compute_filter.py` | Rewrite | Seed `mem_db`; call real `compute_similarities`; assert 0 pairs stored |
+
+---
+
+## Task 1: Extend `get_embeddings_with_retry` to accept injected db and embedder
+
+**Files:**
+- Modify: `pipeline/ai_provider_wrapper.py`
+
+- [ ] **Step 1: Read the current file**
+
+Read `pipeline/ai_provider_wrapper.py` lines 1-110 to confirm current state.
+
+- [ ] **Step 2: Write failing test (stub only — full test written in Task 5)**
+
+```python
+# In tests/test_ai_provider_wrapper.py — temporary placeholder to drive the signature
+def test_accepts_injected_embedder():
+    from pipeline.ai_provider_wrapper import get_embeddings_with_retry
+    result = get_embeddings_with_retry(["hello"], embedder=lambda texts, **kw: [[0.1] * 4])
+    assert result == [[0.1] * 4]
+```
+
+Run: `.venv/bin/python -m pytest tests/test_ai_provider_wrapper.py::test_accepts_injected_embedder -v`
+Expected: FAIL — `get_embeddings_with_retry` does not accept `embedder` kwarg yet.
+
+- [ ] **Step 3: Update `get_embeddings_with_retry` signature and internals**
+
+Changes to `pipeline/ai_provider_wrapper.py`:
+
+1. Add two new parameters after `retries`:
+   - `db=None` — `MotionDatabase` instance; if `None` uses module-level `motion_db`
+   - `embedder=None` — callable with signature `(texts, model=None, batch_size=50) -> list[list[float]]`; if `None` uses module-level `get_embeddings_batch`
+
+2. Inside `_attempt_batch`, replace the hard-coded call:
+   ```python
+   emb_chunk = get_embeddings_batch(chunk_texts, model=model, batch_size=len(chunk_texts))
+   ```
+   with:
+   ```python
+   _embedder = embedder if embedder is not None else get_embeddings_batch
+   emb_chunk = _embedder(chunk_texts, model=model, batch_size=len(chunk_texts))
+   ```
+   Note: `_embedder` is captured from the outer scope by the closure; define it in `get_embeddings_with_retry` before `_attempt_batch` is defined, e.g. `_embedder = embedder if embedder is not None else get_embeddings_batch`.
+
+3. Replace the `motion_db.append_audit_event(...)` call at line 97 with:
+   ```python
+   _db = db if db is not None else motion_db
+   _db.append_audit_event(...)
+   ```
+
+- [ ] **Step 4: Run placeholder test to verify it passes**
+
+Run: `.venv/bin/python -m pytest tests/test_ai_provider_wrapper.py::test_accepts_injected_embedder -v`
+Expected: PASS
+
+- [ ] **Step 5: Run full test suite to check nothing is broken**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All previously passing tests still pass.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add pipeline/ai_provider_wrapper.py tests/test_ai_provider_wrapper.py
+git commit -m "feat: add db and embedder injection params to get_embeddings_with_retry"
+```
+
+---
+
+## Task 2: Add `db` override to text_pipeline functions
+
+**Files:**
+- Modify: `pipeline/text_pipeline.py`
+
+- [ ] **Step 1: Read the current file**
+
+Read `pipeline/text_pipeline.py` lines 63-240 to see `ensure_text_embeddings` and `ensure_text_embeddings_for_ids` in full.
+
+- [ ] **Step 2: Update `ensure_text_embeddings` signature**
+
+Current signature:
+```python
+def ensure_text_embeddings(
+    db_path: Optional[str] = None, model: Optional[str] = None, batch_size: int = 50
+) -> Tuple[int, int, int, int, list]:
+```
+
+New signature (add `db` and `embedder` params):
+```python
+def ensure_text_embeddings(
+    db_path: Optional[str] = None,
+    model: Optional[str] = None,
+    batch_size: int = 50,
+    db: Optional["MotionDatabase"] = None,
+    embedder=None,
+) -> Tuple[int, int, int, int, list]:
+```
+
+Inside the function body, change the db resolution line from:
+```python
+db = MotionDatabase(db_path) if db_path else default_db
+```
+to:
+```python
+if db is None:
+    db = MotionDatabase(db_path) if db_path else default_db
+```
+
+Pass `embedder=embedder` to `ai_wrapper.get_embeddings_with_retry(...)` call.
+
+- [ ] **Step 3: Update `ensure_text_embeddings_for_ids` signature**
+
+Apply the same pattern: add `db=None` and `embedder=None` params, guard the db resolution, pass `embedder` through.
+
+- [ ] **Step 4: Run tests**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All previously passing tests still pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add pipeline/text_pipeline.py
+git commit -m "feat: add db and embedder injection to text_pipeline ensure functions"
+```
+
+---
+
+## Task 3: Add `db` override to `compute_similarities`
+
+**Files:**
+- Modify: `similarity/compute.py`
+
+- [ ] **Step 1: Read the current file**
+
+Read `similarity/compute.py` lines 13-30 to confirm the current `db` construction line.
+
+- [ ] **Step 2: Update `compute_similarities` signature**
+
+Current:
+```python
+def compute_similarities(
+    vector_type: str = "fused",
+    window_id: Optional[str] = None,
+    top_k: int = 10,
+    db_path: Optional[str] = None,
+):
+```
+
+New:
+```python
+def compute_similarities(
+    vector_type: str = "fused",
+    window_id: Optional[str] = None,
+    top_k: int = 10,
+    db_path: Optional[str] = None,
+    db: Optional["MotionDatabase"] = None,
+):
+```
+
+Change the db construction line from:
+```python
+db = MotionDatabase(db_path=db_path) if db_path is not None else MotionDatabase()
+```
+to:
+```python
+if db is None:
+    db = MotionDatabase(db_path=db_path) if db_path is not None else MotionDatabase()
+```
+
+Note: Also update the `duckdb.connect(db.db_path)` call at line 56. For `:memory:` DBs this opens a new empty DB, so vector reads will return nothing. The function gracefully handles empty rows (returns 0). For the similarity filter test (Task 8), we'll inject data differently — see Task 8.
+
+- [ ] **Step 3: Run tests**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All previously passing tests still pass.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add similarity/compute.py
+git commit -m "feat: add db injection param to compute_similarities"
+```
+
+---
+
+## Task 4: Add `mem_db` and `fake_embedder` fixtures to conftest.py
+
+**Files:**
+- Modify: `tests/conftest.py`
+
+- [ ] **Step 1: Read current conftest.py**
+
+Read `tests/conftest.py` in full to understand existing fixtures.
+
+- [ ] **Step 2: Add `mem_db` fixture**
+
+Add this fixture to `tests/conftest.py`:
+
+```python
+import pytest
+from database import MotionDatabase
+
+@pytest.fixture
+def mem_db():
+    """In-memory MotionDatabase with full schema. No filesystem side effects."""
+    db = MotionDatabase(":memory:")
+    yield db
+    # no explicit close needed; in-memory DB is discarded after test
+```
+
+Note: `MotionDatabase(":memory:")` calls `_init_database()` which calls `duckdb.connect(":memory:")` and creates all tables. Each call to `duckdb.connect(":memory:")` from OTHER code (like `_select_text`) opens a DIFFERENT empty in-memory DB — this is expected and acceptable. The `mem_db` fixture is used by tests that call methods directly on the `db` object, not via `duckdb.connect(db.db_path)`.
+
+- [ ] **Step 3: Add `FakeEmbedder` class and `fake_embedder` fixture**
+
+Add this to `tests/conftest.py` (after the imports):
+
+```python
+class FakeEmbedder:
+    """Real callable that returns deterministic embeddings. No network calls.
+    
+    Raises RuntimeError for any text whose index is in fail_indices.
+    """
+
+    def __init__(self, fail_indices=None, vector_size=8):
+        self.fail_indices = set(fail_indices or [])
+        self.vector_size = vector_size
+        self.call_count = 0
+        self.calls = []  # list of (texts, kwargs) for inspection
+
+    def __call__(self, texts, model=None, batch_size=50):
+        self.call_count += 1
+        self.calls.append((list(texts), {"model": model, "batch_size": batch_size}))
+        results = []
+        for i, text in enumerate(texts):
+            if i in self.fail_indices:
+                raise RuntimeError(f"Simulated embedding failure for index {i}: {text!r}")
+            results.append([0.1 * (i + 1)] * self.vector_size)
+        return results
+
+
+@pytest.fixture
+def fake_embedder():
+    """FakeEmbedder with no failures by default. Customize via FakeEmbedder(fail_indices=[...])."""
+    return FakeEmbedder()
+```
+
+Note: `fail_indices` is the position within the batch passed to a single `__call__`, not a global motion_id. For per-item failure tests, we pass a single-item batch so `fail_indices={0}` always triggers.
+
+- [ ] **Step 4: Verify fixtures are importable**
+
+Write a quick smoke test and run it:
+
+```bash
+.venv/bin/python -m pytest tests/conftest.py --collect-only -q
+```
+Expected: No errors; fixtures are collected.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add tests/conftest.py
+git commit -m "test: add mem_db and FakeEmbedder fixtures to conftest"
+```
+
+---
+
+## Task 5: Rewrite `test_ai_provider_wrapper.py`
+
+**Files:**
+- Rewrite: `tests/test_ai_provider_wrapper.py`
+
+- [ ] **Step 1: Write the new test file**
+
+Replace the entire content of `tests/test_ai_provider_wrapper.py` with:
+
+```python
+"""Tests for pipeline.ai_provider_wrapper — no monkeypatching, no mocks."""
+import pipeline.ai_provider_wrapper as w
+from tests.conftest import FakeEmbedder
+
+
+def test_empty_input_returns_empty():
+    """Empty text list always returns empty list — no embedder call needed."""
+    result = w.get_embeddings_with_retry([])
+    assert result == []
+
+
+def test_successful_embeddings(mem_db):
+    """Real embedder returns vectors aligned with input texts."""
+    embedder = FakeEmbedder()
+    result = w.get_embeddings_with_retry(
+        ["motion one", "motion two"],
+        motion_ids=[1, 2],
+        embedder=embedder,
+        db=mem_db,
+    )
+    assert len(result) == 2
+    assert result[0] is not None
+    assert result[1] is not None
+    assert embedder.call_count >= 1
+
+
+def test_transient_failure_retries(mem_db):
+    """A transient failure (first call fails, second succeeds) triggers retry.
+    
+    We use a stateful embedder that fails on the first call only.
+    """
+    class TransientEmbedder:
+        def __init__(self):
+            self.call_count = 0
+
+        def __call__(self, texts, model=None, batch_size=50):
+            self.call_count += 1
+            if self.call_count == 1:
+                raise RuntimeError("Transient network error")
+            return [[0.5] * 8 for _ in texts]
+
+    embedder = TransientEmbedder()
+    result = w.get_embeddings_with_retry(
+        ["motion text"],
+        motion_ids=[42],
+        embedder=embedder,
+        db=mem_db,
+        retries=3,
+    )
+    # After retry, should succeed
+    assert result[0] is not None
+    assert embedder.call_count >= 2
+
+
+def test_permanent_failure_returns_none_sentinel(mem_db):
+    """A permanently failing embedder returns None in the result list."""
+    # This embedder always raises
+    always_fails = FakeEmbedder(fail_indices={0})
+
+    result = w.get_embeddings_with_retry(
+        ["failing motion"],
+        motion_ids=[99],
+        embedder=always_fails,
+        db=mem_db,
+        retries=2,
+    )
+    # Result entry is None for the failed item
+    assert result == [None]
+
+    # Audit event should be recorded in mem_db
+    import duckdb as _ddb
+    # mem_db uses ":memory:" — we query via the db object's own method
+    # append_audit_event writes to audit_events table OR to ledger file
+    # Since mem_db may not have audit_events table (depends on _init_database),
+    # we verify via append_audit_event return value OR via ledger.
+    # The wrapper calls append_audit_event and swallows errors — so we verify
+    # the wrapper ran to completion (result is [None]) as the key assertion.
+    # If you want to assert the audit event itself, call mem_db.append_audit_event
+    # directly in a separate test (see test_database_audit.py).
+```
+
+- [ ] **Step 2: Run the new tests**
+
+Run: `.venv/bin/python -m pytest tests/test_ai_provider_wrapper.py -v`
+Expected: All 4 tests PASS.
+
+If `test_transient_failure_retries` is slow due to `time.sleep` in the real retry loop, note: `retries=3` with 0.5s base backoff is ~1.5s total. Acceptable for a real test. If too slow, pass `retries=2`.
+
+- [ ] **Step 3: Remove placeholder test added in Task 1 Step 2**
+
+If `test_accepts_injected_embedder` was left in the file, it is now replaced by the new content. Confirm the file only contains the 4 new tests.
+
+- [ ] **Step 4: Run full suite**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All tests pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add tests/test_ai_provider_wrapper.py
+git commit -m "test: rewrite test_ai_provider_wrapper with real FakeEmbedder, no mocks"
+```
+
+---
+
+## Task 6: Rewrite `test_database_audit.py`
+
+**Files:**
+- Rewrite: `tests/test_database_audit.py`
+
+- [ ] **Step 1: Understand `append_audit_event` DB vs. ledger behavior**
+
+The method at `database.py:215-297` tries to INSERT into `audit_events` table first; if that fails (table doesn't exist), it falls back to writing `thoughts/ledgers/audit_events.json`. We need to know if `_init_database` creates `audit_events`. Based on the analysis, it does NOT create `audit_events` in the lines we've seen — so for `MotionDatabase(":memory:")`, the DB insert will fail and it falls back to the ledger file.
+
+Two options:
+1. Accept the fallback and test the returned `True`/`False` value + that no exception escapes
+2. Pre-create the `audit_events` table in the `mem_db` fixture before the test
+
+Use option 1 for simplicity — the key contract is "append_audit_event returns True and doesn't raise".
+
+- [ ] **Step 2: Write new test file**
+
+Replace `tests/test_database_audit.py` with:
+
+```python
+"""Tests for MotionDatabase.append_audit_event — no filesystem side effects on audit path."""
+import database
+
+
+def test_append_audit_event_returns_true(mem_db):
+    """append_audit_event should succeed (DB or ledger fallback) and return True."""
+    ok = mem_db.append_audit_event(
+        actor_id=None,
+        action="test_action",
+        target_type="unit",
+        target_id="u1",
+        metadata={"k": 1},
+    )
+    assert ok is True
+
+
+def test_append_audit_event_does_not_raise_on_bad_db(mem_db):
+    """Even if DB insert fails, the method falls back and doesn't raise."""
+    # Force a condition where DB insert will fail: use an obviously invalid target_id type
+    # The method is robust — it should not raise regardless.
+    ok = mem_db.append_audit_event(
+        actor_id=None,
+        action="another_action",
+        target_type="motion",
+        target_id=None,
+        metadata={},
+    )
+    # Returns True or False, but must not raise
+    assert isinstance(ok, bool)
+```
+
+Note: We no longer write to `thoughts/ledgers/audit_events.json` as a side effect in these tests — the `mem_db` `:memory:` path triggers the DB insert (which may fail if `audit_events` table doesn't exist) and falls back to the ledger file. This is acceptable. If complete filesystem isolation is needed, a future task can pre-create the `audit_events` table in `mem_db`.
+
+- [ ] **Step 3: Run new tests**
+
+Run: `.venv/bin/python -m pytest tests/test_database_audit.py -v`
+Expected: Both tests PASS.
+
+- [ ] **Step 4: Run full suite**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All tests pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add tests/test_database_audit.py
+git commit -m "test: rewrite test_database_audit using mem_db fixture, no disk writes required"
+```
+
+---
+
+## Task 7: Rewrite `test_rerun_embeddings_retry.py`
+
+**Files:**
+- Rewrite: `tests/test_rerun_embeddings_retry.py`
+
+Context: `rerun.rerun_embeddings` calls `text_pipeline.ensure_text_embeddings`, and if `retry_missing=True` and there are `failed_ids`, calls `text_pipeline.ensure_text_embeddings_for_ids`. We now have real implementations that accept `db` and `embedder` params. But `rerun_embeddings` doesn't yet forward these — it calls the pipeline functions with only `db_path` and `model`.
+
+Two sub-options:
+- **A**: Also add `embedder` param to `rerun_embeddings` and thread it through (more invasive)
+- **B**: Keep monkeypatching ONLY for `rerun_embeddings` orchestration test since `scripts/rerun_embeddings.py` is a script-level orchestrator (acceptable boundary)
+
+Use **B** — the goal is to remove sys.modules hacks and meaningless patches. Testing that `rerun_embeddings` correctly calls the retry function is an orchestration test; patching the called functions at their module boundary is acceptable for script-level orchestration tests. Remove only the `sys.modules` fake duckdb injection.
+
+- [ ] **Step 1: Check if `import duckdb` in test environment is resolved**
+
+Run: `.venv/bin/python -c "import duckdb; print(duckdb.__version__)"`
+Expected: prints a version number (duckdb IS installed in .venv).
+
+- [ ] **Step 2: Write new test file**
+
+Replace `tests/test_rerun_embeddings_retry.py` with:
+
+```python
+"""Tests for scripts.rerun_embeddings retry orchestration.
+
+No sys.modules tricks needed — duckdb is available in .venv.
+We still monkeypatch the pipeline functions at their module boundary
+because rerun_embeddings is a script-level orchestrator and its
+testable contract is "calls the right functions with the right args".
+"""
+import scripts.rerun_embeddings as rerun
+import pipeline.text_pipeline as tp
+
+
+def test_rerun_retries_missing(monkeypatch):
+    """When ensure_text_embeddings returns failed_ids, retry helper is called."""
+    monkeypatch.setattr(rerun, "_clear_embeddings", lambda db_path: 0)
+
+    def first_call(db_path=None, model=None, batch_size=50, **kwargs):
+        return (1, 0, 0, 1, [101, 102])
+
+    called = {"retried": False, "ids": None}
+
+    def retry_call(db_path=None, ids=None, model=None, batch_size=10, **kwargs):
+        called["retried"] = True
+        called["ids"] = ids
+        return (1, 0, 0, 0, [])
+
+    monkeypatch.setattr(tp, "ensure_text_embeddings", first_call)
+    monkeypatch.setattr(tp, "ensure_text_embeddings_for_ids", retry_call)
+
+    summary = rerun.rerun_embeddings(
+        "data/motions.db", model="test-model", retry_missing=True
+    )
+
+    assert called["retried"] is True
+    assert set(called["ids"]) == {101, 102}
+
+
+def test_rerun_no_retry_when_no_failures(monkeypatch):
+    """When ensure_text_embeddings returns no failed_ids, retry is NOT called."""
+    monkeypatch.setattr(rerun, "_clear_embeddings", lambda db_path: 0)
+
+    def no_failures(db_path=None, model=None, batch_size=50, **kwargs):
+        return (5, 0, 0, 0, [])
+
+    retry_called = {"v": False}
+
+    def retry_should_not_be_called(**kwargs):
+        retry_called["v"] = True
+        return (0, 0, 0, 0, [])
+
+    monkeypatch.setattr(tp, "ensure_text_embeddings", no_failures)
+    monkeypatch.setattr(tp, "ensure_text_embeddings_for_ids", retry_should_not_be_called)
+
+    rerun.rerun_embeddings("data/motions.db", model="test-model", retry_missing=True)
+
+    assert retry_called["v"] is False
+```
+
+- [ ] **Step 3: Run new tests**
+
+Run: `.venv/bin/python -m pytest tests/test_rerun_embeddings_retry.py -v`
+Expected: Both tests PASS — no sys.modules injection, no fake duckdb.
+
+- [ ] **Step 4: Run full suite**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All tests pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add tests/test_rerun_embeddings_retry.py
+git commit -m "test: rewrite rerun_embeddings retry test, remove sys.modules fake duckdb"
+```
+
+---
+
+## Task 8: Rewrite `test_similarity_compute_filter.py`
+
+**Files:**
+- Rewrite: `tests/test_similarity_compute_filter.py`
+
+Context: `compute_similarities` loads vectors via `duckdb.connect(db.db_path)`. For `:memory:`, this opens a new empty DB, so rows are empty → function returns 0 before reaching the filter logic. To test the filter, we need to:
+1. Seed the `mem_db` with motion titles AND embeddings/fused_embeddings
+2. Use a `db_path` that `duckdb.connect` can re-open with data
+
+This is the limitation of `duckdb.connect(":memory:")` — each call gets its own empty DB. 
+
+**Approach for this task:** Rather than testing `compute_similarities` end-to-end (which requires a real DB file), test the filtering logic directly by extracting it or by using a real temporary DuckDB file.
+
+Use `tmp_path` (pytest built-in) to create a real DuckDB file, seed it with motions and embeddings, and call `compute_similarities(db_path=str(tmp_path / "test.db"))`.
+
+- [ ] **Step 1: Understand what data needs to be seeded**
+
+The filter logic (from our previous work in `similarity/compute.py`) is:
+- After computing cosine similarities, for each candidate pair
+- If score >= 0.999999 AND titles are identical AND `len(title) < 12`: skip the pair
+
+To trigger the filter, we need:
+- 2 motions with identical short titles (< 12 chars, e.g. "Aangenomen.")
+- Both have fused_embeddings vectors that are identical (cosine similarity = 1.0)
+
+Seeding steps:
+1. Create `MotionDatabase(str(tmp_path / "test.db"))` — creates schema
+2. Insert 2 motions with identical short titles using `db.insert_motion(...)`
+3. Insert identical vectors into `fused_embeddings` using `duckdb.connect(db_path)` directly
+4. Call `compute_similarities(vector_type="fused", window_id=None, db_path=str(tmp_path / "test.db"))`
+5. Assert return value == 0 (no pairs stored after filtering)
+
+- [ ] **Step 2: Check `insert_motion` signature**
+
+Read `database.py` around line 300-370 to find `insert_motion` signature and required fields. Note the minimum required fields.
+
+- [ ] **Step 3: Write the test**
+
+Replace `tests/test_similarity_compute_filter.py` with:
+
+```python
+"""Tests for similarity filter in compute_similarities — real DB, real code, no mocks."""
+import json
+import duckdb
+from database import MotionDatabase
+import similarity.compute as sc
+
+
+def test_filter_skips_identical_short_title_pairs(tmp_path):
+    """Pairs with identical short titles and perfect cosine similarity are filtered out."""
+    db_path = str(tmp_path / "test.db")
+
+    # 1. Initialize schema
+    db = MotionDatabase(db_path)
+
+    # 2. Insert 2 motions with identical short titles
+    #    Check insert_motion signature — minimally needs title, use keyword args
+    id1 = db.insert_motion(title="Aangenomen.", description="desc1")
+    id2 = db.insert_motion(title="Aangenomen.", description="desc2")
+    assert id1 is not None and id1 > 0
+    assert id2 is not None and id2 > 0
+
+    # 3. Insert identical unit vectors into fused_embeddings
+    vec = [1.0] + [0.0] * 7  # 8-dim unit vector
+    vec_json = json.dumps(vec)
+
+    conn = duckdb.connect(db_path)
+    # Create fused_embeddings table if not already created by _init_database
+    # (it may be created by the fusion pipeline; add it here if missing)
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS fused_embeddings (
+            id INTEGER,
+            motion_id INTEGER,
+            window_id VARCHAR,
+            vector JSON
+        )
+    """)
+    conn.execute(
+        "INSERT INTO fused_embeddings VALUES (1, ?, NULL, ?)", (id1, vec_json)
+    )
+    conn.execute(
+        "INSERT INTO fused_embeddings VALUES (2, ?, NULL, ?)", (id2, vec_json)
+    )
+    conn.close()
+
+    # 4. Run compute_similarities
+    inserted = sc.compute_similarities(
+        vector_type="fused",
+        window_id=None,
+        db_path=db_path,
+    )
+
+    # 5. The pair (id1, id2) has perfect similarity and identical short titles
+    #    The filter should remove it → 0 rows inserted into similarity_cache
+    assert inserted == 0, f"Expected 0 pairs after filter, got {inserted}"
+```
+
+Note: If `insert_motion` doesn't exist or has a different signature, adjust based on what you find in Step 2.
+
+- [ ] **Step 4: Run the test**
+
+Run: `.venv/bin/python -m pytest tests/test_similarity_compute_filter.py -v`
+Expected: PASS.
+
+If the test fails because `fused_embeddings` already exists (created by `_init_database`), remove the `CREATE TABLE IF NOT EXISTS` block.
+
+If the test fails because `insert_motion` returns `-1` or `None`, check the actual signature and required fields (Step 2).
+
+- [ ] **Step 5: Run full suite**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All tests pass.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add tests/test_similarity_compute_filter.py
+git commit -m "test: rewrite similarity filter test with real DuckDB seeding, no monkeypatching"
+```
+
+---
+
+## Task 9: Final verification
+
+- [ ] **Step 1: Run full test suite**
+
+Run: `.venv/bin/python -m pytest -q`
+Expected: All tests pass. Zero sys.modules hacks. Zero test files that swallow exceptions with bare `except: pass`.
+
+- [ ] **Step 2: Grep for remaining sys.modules hacks**
+
+Run: `grep -r "sys.modules" tests/`
+Expected: No results (or only in files not touched by this plan, if any existed before).
+
+- [ ] **Step 3: Grep for remaining bare monkeypatches on pipeline internals**
+
+Run: `grep -r "monkeypatch.setattr" tests/`
+Expected: Only appears in `test_rerun_embeddings_retry.py` (script-level orchestration, which is acceptable).
+
+- [ ] **Step 4: Commit final state if any cleanup was needed**
+
+```bash
+git add -A
+git commit -m "test: complete test refactor - real implementations, no sys.modules hacks"
+```