Add integration test

ui-tests/tests/nbdime-merge-test10.spec.ts

@@ -0,0 +1,28 @@
+import { expect, test } from '@playwright/test';
+
+test.beforeEach(async ({ page }) => {
+  await page.goto('http://localhost:41000/merge');
+  await page.locator('#merge-local').fill('data/merge_test10/left.ipynb');
+  await page.locator('#merge-base').fill('data/merge_test10/center.ipynb');
+  await page.locator('#merge-remote').fill('data/merge_test10/right.ipynb');
+  await page.getByRole('button', { name: 'Merge files' }).click();
+});
+
+/* notebooks of same length and 1 conflict*/
+test.describe('merge test10', () => {
+  test('should synchronize the collapse status between editor', async ({ page }) => {
+    expect.soft(await page.locator('#main').screenshot()).toMatchSnapshot();
+
+    // Should display 4 collapsers
+    const collapsers = page.getByText('4 unchanged lines');
+    await expect.soft(collapsers).toHaveCount(4);
+    await expect.soft(page.getByText('gaussian array y')).toHaveCount(0);
+
+    // Click on the base editor collapser
+    await page.getByText('4 unchanged lines').nth(1).click();
+
+    // Should not display any collapsers
+    await expect.soft(collapsers).toHaveCount(0);
+    await expect(page.getByText('gaussian array y')).toHaveCount(4);
+  });
+});