Function mockScrollEl

tests/hold-stream.test.ts:118–131

(scrollTop: number, scrollHeight: number, clientHeight: number)

describe("syncStreamScrollFollow", () => {
  function mockScrollEl(scrollTop: number, scrollHeight: number, clientHeight: number) {
    const el = document.createElement("div");
    let top = scrollTop;
    Object.defineProperty(el, "scrollTop", {
      configurable: true,
      get: () => top,
      set: (value: number) => {
        top = value;
      },
    });
    Object.defineProperty(el, "scrollHeight", { configurable: true, value: scrollHeight });
    Object.defineProperty(el, "clientHeight", { configurable: true, value: clientHeight });
    return el;
  }

  it("pauses when the reader scrolls up", () => {
    const el = mockScrollEl(100, 1000, 400);