Problem

The browser test <DataGridPro /> - Rows > virtualization > Pagination > should render only the pageSize fails intermittently in CI (for example CircleCI build https://circleci.com/gh/mui/mui-x/877236, which surfaced on the unrelated Renovate PR #23083 that only bumps @tanstack/query in the docs):

AssertionError: expected div.MuiDataGrid-cell...[title="7"] to have text '31', but the text was '7'

Cause

The test scrolls the virtual scroller to the bottom and then asserts the last rendered cell synchronously, with no waitFor:

await act(async () => virtualScroller.scrollTo({ top: 2000 }));
const lastCell = ...;
expect(lastCell).to.have.text('31');

scrollTo updates scrollTop synchronously, but the browser dispatches the native scroll event asynchronously. The grid updates its render context only from that event (handleScroll -> triggerUpdateRenderContext -> ReactDOM.flushSync). When the assertion runs before the scroll event fires, the DOM still shows the initial top window, so the last cell reads its initial value (7) instead of the expected 31. Under CI load the event is sometimes late, hence the flake.

The sibling test should not virtualize the last page if smaller than viewport is not affected: its last page fits within the viewport, so the scroll is clamped to 0 and no re-render is needed.

Fix

Wrap the assertion in waitFor, matching the convention already used by every other scroll test in this file.

Test plan

Ran the browser test suite for the file locally; the target test and the full rows.DataGridPro.test.tsx (47 tests) pass.

🤖 Generated with Claude Code