feat(excel): group entries by date, join names with ' & '

tests/excel.test.mjs

@@ -0,0 +1,67 @@
+import assert from 'node:assert/strict';
+import { buildScheduleColumns } from '../js/excel.js';
+
+const employees = [
+  { id: 'a1', name: 'Anna Müller' },
+  { id: 'b1', name: 'Bernd Schulz' },
+  { id: 'c1', name: 'Carla Weber' }
+];
+
+// Single employee per day
+{
+  const assignments = [
+    { date: '2026-04-01', employeeId: 'a1' },
+    { date: '2026-04-02', employeeId: 'b1' }
+  ];
+  const cols = buildScheduleColumns(assignments, employees);
+  assert.deepEqual(cols.names, ['Anna Müller', 'Bernd Schulz'], 'names per single-entry day');
+  assert.deepEqual(cols.dates, ['01.04.2026', '02.04.2026'], 'dates formatted DD.MM.YYYY');
+}
+
+// Two employees per day → joined with " & ", alphabetical
+{
+  const assignments = [
+    { date: '2026-04-01', employeeId: 'b1' },  // Bernd inserted first
+    { date: '2026-04-01', employeeId: 'a1' }   // Anna inserted second
+  ];
+  const cols = buildScheduleColumns(assignments, employees);
+  assert.equal(cols.names.length, 1, 'one column per date');
+  assert.equal(cols.names[0], 'Anna Müller & Bernd Schulz', 'names alphabetical, joined with " & "');
+  assert.equal(cols.dates[0], '01.04.2026', 'one date entry');
+}
+
+// Three employees per day
+{
+  const assignments = [
+    { date: '2026-04-01', employeeId: 'c1' },
+    { date: '2026-04-01', employeeId: 'a1' },
+    { date: '2026-04-01', employeeId: 'b1' }
+  ];
+  const cols = buildScheduleColumns(assignments, employees);
+  assert.equal(cols.names[0], 'Anna Müller & Bernd Schulz & Carla Weber', 'three names joined alphabetical');
+}
+
+// Multiple dates with multiple employees, dates ascending
+{
+  const assignments = [
+    { date: '2026-04-02', employeeId: 'a1' },
+    { date: '2026-04-01', employeeId: 'b1' },
+    { date: '2026-04-01', employeeId: 'a1' }
+  ];
+  const cols = buildScheduleColumns(assignments, employees);
+  assert.deepEqual(cols.dates, ['01.04.2026', '02.04.2026'], 'dates sorted ascending');
+  assert.deepEqual(cols.names, ['Anna Müller & Bernd Schulz', 'Anna Müller'], 'names per column in date order');
+}
+
+// Unknown employeeId: empty string slot, sorted with other names
+{
+  const assignments = [
+    { date: '2026-04-01', employeeId: 'a1' },
+    { date: '2026-04-01', employeeId: 'unknown' }
+  ];
+  const cols = buildScheduleColumns(assignments, employees);
+  // Empty-string sorts before 'Anna Müller'
+  assert.equal(cols.names[0], ' & Anna Müller', 'unknown employee → empty string in join');
+}
+
+console.log('All excel tests passed.');