test: add regression guards for the bug classes fixed in this PR

Three lightweight static checks, all enrolled in CI's unit-test
allowlist along with the new web-cache test:

- test_template_targets.py: every literal render_template() target must
  exist (would have caught the weather/stocks partial 500s at commit
  time).
- test_widget_scripts.py: every widget JS file must be script-included
  in base.html or explicitly allowlisted with a reason (would have
  caught the unloaded time-picker/file-upload-single/plugin-file-manager
  widgets), and allowlisted files must NOT be included (prevents the
  example widget from shadowing the real color-picker).
- test_doc_links.py: relative markdown links in active docs must
  resolve (docs/archive/ exempt).

Each guard was verified to fail against the pre-PR tree and pass now.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SXb4mKcAkVaxkeTb3YnAdr

test/test_doc_links.py

@@ -0,0 +1,40 @@
+"""Guard: relative markdown links in active docs must resolve.
+
+Scans repo-root *.md and docs/ (excluding docs/archive/, which is allowed
+to rot). External URLs, mailto links, and pure anchors are skipped, as are
+links inside fenced code blocks.
+"""
+import re
+from pathlib import Path
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent
+LINK_RE = re.compile(r'\[[^\]]*\]\(([^)\s]+)\)')
+FENCE_RE = re.compile(r'^(```|~~~)')
+
+
+def _md_files():
+    yield from PROJECT_ROOT.glob('*.md')
+    for path in PROJECT_ROOT.glob('docs/**/*.md'):
+        if 'archive' not in path.parts:
+            yield path
+
+
+def test_relative_markdown_links_resolve():
+    broken = []
+    for md in _md_files():
+        in_fence = False
+        for lineno, line in enumerate(md.read_text(encoding='utf-8').splitlines(), 1):
+            if FENCE_RE.match(line.strip()):
+                in_fence = not in_fence
+                continue
+            if in_fence:
+                continue
+            for target in LINK_RE.findall(line):
+                if target.startswith(('http://', 'https://', 'mailto:', '#')):
+                    continue
+                resolved = (md.parent / target.split('#')[0]).resolve()
+                if not resolved.exists():
+                    broken.append(
+                        f'{md.relative_to(PROJECT_ROOT)}:{lineno} -> {target}'
+                    )
+    assert not broken, 'Broken relative markdown links:\n' + '\n'.join(broken)

test/test_template_targets.py

@@ -0,0 +1,33 @@
+"""Guard: every literal render_template() target must exist on disk.
+
+Catches routes that reference templates deleted in a refactor (a real bug
+class: the weather/stocks partials 500'd for months because their
+templates were removed when those displays became plugins).
+"""
+import re
+from pathlib import Path
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent
+TEMPLATE_ROOT = PROJECT_ROOT / 'web_interface' / 'templates'
+RENDER_RE = re.compile(r"""render_template\(\s*['"]([^'"]+)['"]""")
+
+
+def _python_sources():
+    yield PROJECT_ROOT / 'web_interface' / 'app.py'
+    yield from (PROJECT_ROOT / 'web_interface' / 'blueprints').glob('*.py')
+
+
+def test_all_literal_render_template_targets_exist():
+    missing = []
+    for source in _python_sources():
+        text = source.read_text(encoding='utf-8')
+        for lineno, line in enumerate(text.splitlines(), 1):
+            for target in RENDER_RE.findall(line):
+                if not (TEMPLATE_ROOT / target).is_file():
+                    missing.append(
+                        f'{source.relative_to(PROJECT_ROOT)}:{lineno} -> {target}'
+                    )
+    assert not missing, (
+        'render_template() references templates that do not exist under '
+        f'web_interface/templates/:\n' + '\n'.join(missing)
+    )

test/test_widget_scripts.py

@@ -0,0 +1,48 @@
+"""Guard: every widget JS file must be loaded by base.html or explicitly allowlisted.
+
+Widget files register themselves with LEDMatrixWidgets at load time; a file
+that exists but is never <script>-included silently breaks any plugin whose
+config schema declares that widget (the field renders as an empty container
+that polls the registry forever). base.html's widget list is maintained by
+hand, so this test keeps it honest.
+"""
+from pathlib import Path
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent
+WIDGETS_DIR = PROJECT_ROOT / 'web_interface' / 'static' / 'v3' / 'js' / 'widgets'
+BASE_HTML = PROJECT_ROOT / 'web_interface' / 'templates' / 'v3' / 'base.html'
+
+# Files that must NOT be script-included, with the reason.
+ALLOWLIST = {
+    # Documentation example (docs/widget-guide.md); registers the name
+    # 'color-picker' and would shadow the real color-picker.js if loaded.
+    'example-color-picker.js',
+}
+
+
+def test_every_widget_script_is_included_in_base_html():
+    base_html = BASE_HTML.read_text(encoding='utf-8')
+    missing = []
+    for js_file in sorted(WIDGETS_DIR.glob('*.js')):
+        if js_file.name in ALLOWLIST:
+            continue
+        if f'v3/js/widgets/{js_file.name}' not in base_html:
+            missing.append(js_file.name)
+    assert not missing, (
+        'Widget files exist but are never <script>-included in base.html '
+        '(plugins declaring these widgets get blank config fields): '
+        + ', '.join(missing)
+        + '. Add a script tag to base.html or add the file to ALLOWLIST '
+        'with a reason.'
+    )
+
+
+def test_allowlisted_widgets_are_not_included():
+    base_html = BASE_HTML.read_text(encoding='utf-8')
+    wrongly_included = [
+        name for name in ALLOWLIST if f'v3/js/widgets/{name}' in base_html
+    ]
+    assert not wrongly_included, (
+        'Allowlisted (must-not-load) widget files are script-included in '
+        'base.html: ' + ', '.join(wrongly_included)
+    )