源码快照 @ 2026-09-02 (source-only, 剔除非源码素材)

apps/app/tests/live-step-scroll.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, test } from "bun:test";
+
+import {
+  isLiveStepAtBottom,
+  pinnedAfterUserScroll,
+  pinnedAfterWheel,
+  shouldFollowLiveStepGrowth,
+} from "../src/components/chat/live-step-scroll";
+
+describe("live step scroll", () => {
+  test("follows streaming growth only while the user is pinned to the tail", () => {
+    expect(shouldFollowLiveStepGrowth({ isLive: true, pinned: true })).toBe(true);
+    expect(shouldFollowLiveStepGrowth({ isLive: true, pinned: false })).toBe(false);
+    expect(shouldFollowLiveStepGrowth({ isLive: false, pinned: true })).toBe(false);
+  });
+
+  test("a wheel-up gesture unpins even when the list is still at the bottom", () => {
+    expect(pinnedAfterWheel({ deltaY: -12, pinned: true, atBottom: true })).toBe(false);
+    expect(pinnedAfterUserScroll(false)).toBe(false);
+    expect(pinnedAfterUserScroll(true)).toBe(true);
+  });
+
+  test("treats a small tail gap as still at the bottom", () => {
+    expect(isLiveStepAtBottom({ scrollHeight: 800, scrollTop: 284, clientHeight: 520 })).toBe(true);
+    expect(isLiveStepAtBottom({ scrollHeight: 800, scrollTop: 100, clientHeight: 520 })).toBe(false);
+  });
+});