@@ -0,0 +1,307 @@
+import {
+  buildTestContext,
+  DocStore,
+  runIdempotencyCheck,
+} from '../testing/migration-idempotency.harness';
+import { codoAddEventType } from './codo-add-event-type.migration';
+
+/** Minimal codo-like config without any event-related entries. */
+function baseSeed(): DocStore {
+  return {
+    'app/Config:CONFIG_ENTITY': {
+      _id: 'Config:CONFIG_ENTITY',
+      data: {
+        navigationMenu: {
+          items: [
+            { entityType: 'Child' },
+            { entityType: 'ChildSchoolRelation' },
+            { entityType: 'Note' },
+            { entityType: 'Todo' },
+          ],
+        },
+        'entity:Note': {
+          label: 'Notiz',
+          attributes: {
+            relatedEntities: {
+              dataType: 'entity',
+              additional: 'ChildSchoolRelation',
+              label: 'Patenschaft/en',
+              isArray: true,
+            },
+          },
+        },
+        'entity:Todo': {
+          label: 'Aufgabe',
+          attributes: {
+            relatedEntities: {
+              dataType: 'entity',
+              additional: ['Child', 'School', 'ChildSchoolRelation'],
+              isArray: true,
+            },
+          },
+        },
+        'view:mentor/:id': {
+          config: {
+            panels: [
+              { title: 'Mentor:in', components: [{ component: 'Form' }] },
+              {
+                title: 'Notizen & Aufgaben',
+                components: [
+                  { component: 'NotesRelatedToEntity' },
+                  { component: 'TodosRelatedToEntity' },
+                ],
+              },
+            ],
+          },
+        },
+        'view:mentee/:id': {
+          config: {
+            panels: [
+              { title: 'Mentee', components: [{ component: 'Form' }] },
+              {
+                title: 'Notizen & Aufgaben',
+                components: [
+                  { component: 'NotesRelatedToEntity' },
+                  { component: 'TodosRelatedToEntity' },
+                ],
+              },
+            ],
+          },
+        },
+        'view:matching': { component: 'MatchingEntities' },
+      },
+    },
+  };
+}
+
+describe('codoAddEventType migration', () => {
+  it('should apply all changes on first run', async () => {
+    const store = baseSeed();
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    expect(result.status).toBe('ok');
+
+    // Enum docs created
+    expect(store['app/ConfigurableEnum:artDerVeranstaltung']).toBeDefined();
+    expect(store['app/ConfigurableEnum:attendance-status']).toBeDefined();
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const config = store['app/Config:CONFIG_ENTITY'] as any;
+
+    // Entity and view configs added
+    expect(config.data['entity:event']).toBeDefined();
+    expect(config.data['entity:event'].label).toBe('Veranstaltung');
+    expect(config.data['view:event']).toBeDefined();
+    expect(config.data['view:event/:id']).toBeDefined();
+
+    // Note relatedEntities updated (string → array with event)
+    expect(
+      config.data['entity:Note'].attributes.relatedEntities.additional,
+    ).toEqual(['ChildSchoolRelation', 'event']);
+
+    // Note relatedEntities label renamed
+    expect(config.data['entity:Note'].attributes.relatedEntities.label).toBe(
+      'Sonstige verknüpfte Datensätze',
+    );
+
+    // Todo relatedEntities updated (array += event)
+    expect(
+      config.data['entity:Todo'].attributes.relatedEntities.additional,
+    ).toEqual(['Child', 'School', 'ChildSchoolRelation', 'event']);
+
+    // Nav menu updated – event inserted before Note
+    const items = config.data.navigationMenu.items;
+    const eventIdx = items.findIndex((i) => i.entityType === 'event');
+    const noteIdx = items.findIndex((i) => i.entityType === 'Note');
+    expect(eventIdx).toBeGreaterThanOrEqual(0);
+    expect(noteIdx).toBeGreaterThan(eventIdx);
+
+    // Veranstaltungen added to mentor view
+    const mentorPanels = config.data['view:mentor/:id'].config.panels;
+    const mentorTab = mentorPanels.find(
+      (p) => p.title === 'Notizen & Aufgaben',
+    );
+    expect(mentorTab.components).toContainEqual(
+      expect.objectContaining({
+        component: 'RelatedEntities',
+        config: expect.objectContaining({ entityType: 'event' }),
+      }),
+    );
+
+    // Veranstaltungen added to mentee view
+    const menteePanels = config.data['view:mentee/:id'].config.panels;
+    const menteeTab = menteePanels.find(
+      (p) => p.title === 'Notizen & Aufgaben',
+    );
+    expect(menteeTab.components).toContainEqual(
+      expect.objectContaining({
+        component: 'RelatedEntities',
+        config: expect.objectContaining({ entityType: 'event' }),
+      }),
+    );
+  });
+
+  it('should be idempotent (second run reports no-change)', async () => {
+    const result = await runIdempotencyCheck(codoAddEventType, baseSeed());
+
+    expect(result.secondRunResult.changed).toBe(false);
+    expect(result.secondRunResult.status).toBe('no-change');
+    expect(result.stateAfterSecondRun).toEqual(result.stateAfterFirstRun);
+  });
+
+  it('should handle missing config document', async () => {
+    const ctx = buildTestContext({});
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.status).toBe('failed');
+    expect(result.changed).toBe(false);
+  });
+
+  it('should handle missing data object in config', async () => {
+    const store: DocStore = {
+      'app/Config:CONFIG_ENTITY': { _id: 'Config:CONFIG_ENTITY' },
+    };
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.status).toBe('failed');
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('no data object'),
+    );
+  });
+
+  it('should skip existing enum docs without overwriting', async () => {
+    const store = baseSeed();
+    store['app/ConfigurableEnum:artDerVeranstaltung'] = {
+      _id: 'ConfigurableEnum:artDerVeranstaltung',
+      values: [{ id: 'CUSTOM', label: 'Custom' }],
+    };
+    store['app/ConfigurableEnum:attendance-status'] = {
+      _id: 'ConfigurableEnum:attendance-status',
+      values: [{ id: 'X', label: 'X' }],
+    };
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true); // Config changes still applied
+
+    // Enum docs untouched
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const artEnum = store['app/ConfigurableEnum:artDerVeranstaltung'] as any;
+    expect(artEnum.values[0].id).toBe('CUSTOM');
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const attEnum = store['app/ConfigurableEnum:attendance-status'] as any;
+    expect(attEnum.values[0].id).toBe('X');
+  });
+
+  it('should skip existing entity:event without overwriting', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    (store['app/Config:CONFIG_ENTITY'] as any).data['entity:event'] = {
+      label: 'Custom Event',
+    };
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true); // Other changes still applied
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const config = store['app/Config:CONFIG_ENTITY'] as any;
+    expect(config.data['entity:event'].label).toBe('Custom Event');
+  });
+
+  it('should handle missing mentor/mentee views with warnings', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const data = (store['app/Config:CONFIG_ENTITY'] as any).data;
+    delete data['view:mentor/:id'];
+    delete data['view:mentee/:id'];
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('view:mentor/:id'),
+    );
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('view:mentee/:id'),
+    );
+  });
+
+  it('should handle missing relatedEntities attribute with warning', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const data = (store['app/Config:CONFIG_ENTITY'] as any).data;
+    delete data['entity:Note'].attributes.relatedEntities;
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('entity:Note'),
+    );
+  });
+
+  it('should handle detail view without matching tab', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const data = (store['app/Config:CONFIG_ENTITY'] as any).data;
+    data['view:mentor/:id'].config.panels = [
+      { title: 'Sonstiges', components: [{ component: 'Form' }] },
+    ];
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('view:mentor/:id'),
+    );
+    expect(result.warnings).toContainEqual(
+      expect.stringContaining('manual review'),
+    );
+  });
+
+  it('should find tab by content-based fallback', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const data = (store['app/Config:CONFIG_ENTITY'] as any).data;
+    // Rename the tab title to something unusual
+    data['view:mentor/:id'].config.panels[1].title = 'Alles Mögliche';
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    // Should still find the tab via content-based fallback
+    const panel = data['view:mentor/:id'].config.panels[1];
+    expect(panel.components).toContainEqual(
+      expect.objectContaining({
+        component: 'RelatedEntities',
+        config: expect.objectContaining({ entityType: 'event' }),
+      }),
+    );
+  });
+
+  it('should append event to end of nav menu when Note is absent', async () => {
+    const store = baseSeed();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const data = (store['app/Config:CONFIG_ENTITY'] as any).data;
+    data.navigationMenu.items = [
+      { entityType: 'Child' },
+      { entityType: 'Todo' },
+    ];
+
+    const ctx = buildTestContext(store);
+    const result = await codoAddEventType.run(ctx);
+
+    expect(result.changed).toBe(true);
+    const items = data.navigationMenu.items;
+    expect(items[items.length - 1]).toEqual({ entityType: 'event' });
+  });
+});