import { describe, expect, it } from "vite-plus/test"; import { resolveWorkGroupScrollAnchor } from "./scrollAnchor.js"; describe("tool-group scroll anchors", () => {  const data = Array.from({ length: 18 }, (_, index) => ({ id: `call-${index}` }));  const state = { data, positionAtIndex: (index: number) => index * 33 };   it("returns to the top after a fast flick even when the cached start is five rows behind", () => {    const snapshot = { ...state, scroll: 0, start: 5 };    expect(resolveWorkGroupScrollAnchor(snapshot)).toEqual({      rowId: "call-0",      offsetWithinRow: 0,      scrollOffset: 0,    });  });   it.each([    { scroll: 302, start: 0, rowId: "call-9", offsetWithinRow: 5 },    { scroll: 40, start: 12, rowId: "call-1", offsetWithinRow: 7 },    { scroll: 165, start: 4, rowId: "call-5", offsetWithinRow: 0 },  ])("uses the measured position at $scroll rather than cached row $start", (example) => {    expect(resolveWorkGroupScrollAnchor({ ...state, ...example })).toEqual({      rowId: example.rowId,      offsetWithinRow: example.offsetWithinRow,      scrollOffset: example.scroll,    });  });   it("preserves an offset within expanded output", () => {    const positions = [0, 33, 600];    expect(      resolveWorkGroupScrollAnchor({        data: [{ id: "first" }, { id: "output" }, { id: "last" }],        scroll: 153,        positionAtIndex: (index) => positions[index],      }),    ).toEqual({ rowId: "output", offsetWithinRow: 120, scrollOffset: 153 });  });   it("does not preserve overscroll before the first row", () => {    expect(resolveWorkGroupScrollAnchor({ ...state, scroll: -20 })).toEqual({      rowId: "call-0",      offsetWithinRow: 0,      scrollOffset: 0,    });  });   it("skips incomplete layout snapshots instead of saving an invalid anchor", () => {    expect(resolveWorkGroupScrollAnchor({ ...state, data: [], scroll: 0 })).toBeUndefined();    expect(resolveWorkGroupScrollAnchor({ ...state, scroll: Number.NaN })).toBeUndefined();    expect(      resolveWorkGroupScrollAnchor({ ...state, scroll: 165, positionAtIndex: () => undefined }),    ).toBeUndefined();    expect(      resolveWorkGroupScrollAnchor({        ...state,        scroll: 165,        positionAtIndex: (index) => (index === 0 ? 0 : Number.NaN),      }),    ).toBeUndefined();  });});