test(coverage): improve backend test coverage and add coverage tooling

- Add coverage>=7.4 to dev dependencies (pyproject.toml, requirements.txt)
- Add 18 new backend tests for low-coverage modules
- Improve api_interpreters.py coverage: 29% → 60% (+31%)
- Improve api_providers.py coverage: 20% → 33% (+13%)
- Improve api_chat.py coverage: 34% → 37% (+3%)
- Overall coverage: 67% → 68%

New tests added:
- test_chat_api.py: 7 new tests (GraphRAG endpoints, history, capabilities)
- test_interpreters_registry_api.py: 4 new tests (toggle, debug endpoints)
- test_providers_api.py: 6 new tests (provider roots, rclone validation)

Coverage tooling:
- Enables local coverage reports: python -m coverage run -m pytest
- Interactive HTML reports: python -m coverage html (htmlcov/index.html)
- Documentation added to dev/prompts.md

Total: 197 tests passing (up from 179)

Author: patchmemory

pyproject.toml

@@ -27,6 +27,7 @@ dev = [
   "playwright==1.40.0",
   "requests>=2.32",
   "beautifulsoup4>=4.12",
+  "coverage>=7.4",
 ]
 
 # Optional LLM provider (only needed if you enable Graphrag LLM features)

requirements.txt

@@ -12,3 +12,4 @@ pytest>=7.4
 pytest-playwright==0.4.3
 playwright==1.40.0
 requests>=2.32
+coverage>=7.4

tests/test_chat_api.py

@@ -1,3 +1,7 @@
+import os
+import pytest
+
+
 def test_api_chat_echo(client):
     # First message
     resp1 = client.post('/api/chat', json={'message': 'Hello'})
@@ -11,3 +15,72 @@ def test_api_chat_echo(client):
     resp2 = client.post('/api/chat', json={'message': 'How are you?'})
     data2 = resp2.get_json()
     assert len(data2['history']) == 4
+
+
+def test_api_chat_missing_message(client):
+    resp = client.post('/api/chat', json={})
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert data['status'] == 'error'
+    assert 'message required' in data['error']
+
+
+def test_api_chat_history(client):
+    # Post a message first
+    client.post('/api/chat', json={'message': 'Test'})
+
+    # Get history
+    resp = client.get('/api/chat/history')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'ok'
+    assert 'history' in data
+    assert len(data['history']) >= 2
+
+
+def test_api_chat_capabilities(client):
+    resp = client.get('/api/chat/capabilities')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'graphrag' in data
+    assert 'enabled' in data['graphrag']
+    assert 'llm_provider' in data['graphrag']
+    assert 'model' in data['graphrag']
+
+
+def test_api_chat_graphrag_disabled_by_default(client):
+    # GraphRAG should be disabled without SCIDK_GRAPHRAG_ENABLED
+    resp = client.post('/api/chat/graphrag', json={'message': 'Test query'})
+    assert resp.status_code == 501
+    data = resp.get_json()
+    assert data['status'] == 'disabled'
+    assert 'SCIDK_GRAPHRAG_ENABLED' in data.get('hint', '')
+
+
+def test_api_chat_graphrag_missing_message(client, monkeypatch):
+    monkeypatch.setenv('SCIDK_GRAPHRAG_ENABLED', '1')
+    resp = client.post('/api/chat/graphrag', json={})
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert data['status'] == 'error'
+    assert 'message required' in data['error']
+
+
+def test_api_chat_context_refresh_disabled(client):
+    resp = client.post('/api/chat/context/refresh')
+    assert resp.status_code == 501
+    data = resp.get_json()
+    assert data['status'] == 'disabled'
+
+
+def test_api_chat_observability_graphrag(client):
+    resp = client.get('/api/chat/observability/graphrag')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'ok'
+    assert 'enabled' in data
+    assert 'llm_provider' in data
+    assert 'model' in data
+    assert 'schema' in data
+    assert 'audit' in data
+    assert isinstance(data['audit'], list)

tests/test_interpreters_registry_api.py

@@ -24,3 +24,43 @@ def test_api_interpreters_schema():
     for it in eff:
         assert 'enabled' in it
         assert 'source' in it
+
+
+def test_api_interpreters_effective_debug(client):
+    resp = client.get('/api/interpreters/effective_debug')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'source' in data
+    assert 'effective_enabled' in data
+    assert 'default_enabled' in data
+    assert 'loaded_settings' in data
+    assert 'env' in data
+    assert isinstance(data['effective_enabled'], list)
+    assert isinstance(data['default_enabled'], list)
+
+
+def test_api_interpreters_toggle_enable(client):
+    # Enable an interpreter
+    resp = client.post('/api/interpreters/csv/toggle', json={'enabled': True})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'updated'
+    assert data['enabled'] is True
+
+
+def test_api_interpreters_toggle_disable(client):
+    # Disable an interpreter
+    resp = client.post('/api/interpreters/csv/toggle', json={'enabled': False})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'updated'
+    assert data['enabled'] is False
+
+
+def test_api_interpreters_toggle_default_enabled(client):
+    # Toggle without explicit enabled flag (defaults to True)
+    resp = client.post('/api/interpreters/python_code/toggle', json={})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['status'] == 'updated'
+    assert data['enabled'] is True

tests/test_providers_api.py

@@ -24,3 +24,62 @@ def test_browse_local_root(client, tmp_path: Path):
     entries = data.get('entries', [])
     names = {e['name'] for e in entries}
     assert 'a.txt' in names
+
+
+def test_provider_roots_default(client):
+    # Test default provider (local_fs)
+    resp = client.get('/api/provider_roots')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert isinstance(data, list)
+    assert len(data) > 0
+    # Validate structure
+    for root in data:
+        assert 'id' in root
+        assert 'name' in root
+        assert 'path' in root
+
+
+def test_provider_roots_specific_provider(client):
+    resp = client.get('/api/provider_roots?provider_id=local_fs')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert isinstance(data, list)
+
+
+def test_provider_roots_invalid_provider(client):
+    resp = client.get('/api/provider_roots?provider_id=nonexistent')
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert 'error' in data
+
+
+def test_rclone_mounts_list(client):
+    # Should return empty list initially (or existing mounts)
+    resp = client.get('/api/rclone/mounts')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert isinstance(data, list)
+
+
+def test_rclone_mounts_create_missing_rclone(client, monkeypatch):
+    # Mock rclone not available
+    monkeypatch.setattr('shutil.which', lambda x: None)
+    resp = client.post('/api/rclone/mounts', json={'remote': 'test:', 'name': 'testmount'})
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert 'rclone not installed' in data['error']
+
+
+def test_rclone_mounts_create_missing_remote(client):
+    resp = client.post('/api/rclone/mounts', json={'name': 'testmount'})
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert 'remote required' in data['error']
+
+
+def test_rclone_mounts_create_missing_name(client):
+    resp = client.post('/api/rclone/mounts', json={'remote': 'test:'})
+    assert resp.status_code == 400
+    data = resp.get_json()
+    assert 'name required' in data['error']