test(export): stale-group + same-date ordinal coverage; comment/guard polish

frontend/tests/ExportDataModal.test.jsx

@@ -110,4 +110,15 @@ describe('ExportDataModal', () => {
     expect(text).toMatch(/^Group,Control,Drug$/m);
     await dl.restore();
   });
+
+  it('a stale/unset group field coerces to None (no Group row in the export)', async () => {
+    const dl = mockDownload();
+    renderModal({ groupField: 'ghost-field' });
+    await screen.findByLabelText('X axis (rows)');
+    await waitFor(() => expect(screen.getByText(/2 rows/i)).toBeInTheDocument());
+    fireEvent.click(screen.getByText('Export CSV'));
+    const text = await readBlobText(dl.getBlob());
+    expect(text).not.toMatch(/^Group,/m);
+    await dl.restore();
+  });
 });

frontend/tests/dataExport.test.js

@@ -237,6 +237,16 @@ describe('buildSampleIndex', () => {
     expect(idx.get('a1').get(250).date).toContain('2026-07-01');
     expect(idx.get('a1').get(260).date).toContain('2026-07-03');
   });
+  it('# days reach counts per-status, not per-distinct-date (same-day statuses get separate ordinals)', () => {
+    const sameDay = [
+      { animal_id: 'z1', date: '2026-07-01T08:00:00Z', analysis_summary: { total: 1 } },
+      { animal_id: 'z1', date: '2026-07-01T20:00:00Z', analysis_summary: { total: 2 } },
+    ];
+    const idx = buildSampleIndex(sameDay, '__days__', []);
+    expect(idx.get('z1').has(1)).toBe(true);
+    expect(idx.get('z1').has(2)).toBe(true);
+    expect(idx.get('z1').has(3)).toBe(false);
+  });
 });
 
 import { buildSubjectSeriesMatrix } from '../src/lib/dataExport';