diff --git a/web/src/shared/lib/session-history.test.ts b/web/src/shared/lib/session-history.test.ts
index 943c2c1..fd47d05 100644
--- a/web/src/shared/lib/session-history.test.ts
+++ b/web/src/shared/lib/session-history.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import { afterMarker, afterPop, afterPush, canGoBack, canGoForward } from './session-history'
 
 describe('历史记录的序号', () => {
@@ -27,3 +27,333 @@ describe('历史记录的序号', () => {
     expect(canGoForward(marked)).toBe(false)
   })
 })
+
+interface HistoryEntry {
+  state: unknown
+  url: string
+}
+
+// 和浏览器一样，后退要到之后的任务才完成：settle() 模拟那一刻的 popstate。
+class FakeHistory {
+  entries: HistoryEntry[]
+  at = 0
+  traversals: number[] = []
+  failure: Error | null = null
+  readonly events = new EventTarget()
+
+  constructor(state: unknown) {
+    this.entries = [{ state, url: '/start' }]
+  }
+
+  get current(): HistoryEntry {
+    return this.entries[this.at] as HistoryEntry
+  }
+
+  get state(): unknown {
+    return this.current.state
+  }
+
+  get urls(): string[] {
+    return this.entries.map(entry => entry.url)
+  }
+
+  pushState(state: unknown, _title: string, url: string): void {
+    if (this.failure)
+      throw this.failure
+    this.entries = [...this.entries.slice(0, this.at + 1), { state, url }]
+    this.at += 1
+  }
+
+  replaceState(state: unknown, _title: string, url?: string): void {
+    if (this.failure)
+      throw this.failure
+    this.entries[this.at] = { state, url: url ?? this.current.url }
+  }
+
+  back(): void {
+    this.traversals.push(-1)
+  }
+
+  settle(): void {
+    const delta = this.traversals.shift()
+    if (delta === undefined)
+      throw new Error('没有等待中的后退')
+    this.pop(delta)
+  }
+
+  pop(delta: number): void {
+    this.at += delta
+    this.events.dispatchEvent(Object.assign(new Event('popstate'), { state: this.state }))
+  }
+
+  press(delta = -1): void {
+    this.pop(delta)
+  }
+}
+
+async function open(state: unknown = null) {
+  vi.resetModules()
+  const history = new FakeHistory(state)
+  vi.stubGlobal('window', {
+    history,
+    location: {
+      get href() {
+        return history.current.url
+      },
+    },
+    addEventListener: (type: string, listener: EventListener) => history.events.addEventListener(type, listener),
+  })
+  const module = await import('./session-history')
+  const log: string[] = []
+  const firstOpen = module.startHistory(() => log.push('notify'))
+  return { ...module, history, log, firstOpen }
+}
+
+afterEach(() => {
+  vi.unstubAllGlobals()
+})
+
+describe('打开页面', () => {
+  it('第一次打开时给当前记录写上序号', async () => {
+    const { firstOpen, history, currentEntry } = await open()
+    expect(firstOpen).toBe(true)
+    expect(history.state).toEqual({ index: 0 })
+    expect(currentEntry().position).toEqual({ index: 0, last: 0 })
+  })
+
+  it('刷新时沿用记录里的序号和标题', async () => {
+    const { firstOpen, history, currentEntry } = await open({ index: 3, title: '房间' })
+    expect(firstOpen).toBe(false)
+    expect(history.state).toEqual({ index: 3, title: '房间' })
+    expect(currentEntry()).toEqual({ position: { index: 3, last: 3 }, title: '房间' })
+  })
+
+  it('刷新时弹窗已经关闭，标记记录改作页面的记录', async () => {
+    const { firstOpen, history } = await open({ index: 2, title: '房间', modal: true })
+    expect(firstOpen).toBe(false)
+    expect(history.state).toEqual({ index: 2, title: '房间' })
+  })
+
+  it.each([
+    ['字符串', 'other'],
+    ['没有序号', {}],
+    ['负数序号', { index: -1 }],
+    ['小数序号', { index: 1.5 }],
+  ])('别的脚本写入的状态（%s）当作第一次打开', async (_, state) => {
+    const { firstOpen, history } = await open(state)
+    expect(firstOpen).toBe(true)
+    expect(history.state).toEqual({ index: 0 })
+  })
+})
+
+describe('写入记录', () => {
+  it('新记录的序号加一，后退和前进由 popstate 同步', async () => {
+    const { writeEntry, currentEntry, history, log } = await open()
+    writeEntry('/a', false, '甲')
+    writeEntry('/b', false)
+    expect(history.urls).toEqual(['/start', '/a', '/b'])
+    expect(currentEntry()).toEqual({ position: { index: 2, last: 2 }, title: undefined })
+
+    history.press()
+    expect(currentEntry()).toEqual({ position: { index: 1, last: 2 }, title: '甲' })
+    expect(log).toEqual(['notify'])
+  })
+
+  it('替换时序号不变，不给标题就沿用原来的', async () => {
+    const { writeEntry, currentEntry, history } = await open({ index: 1, title: '房间' })
+    writeEntry('/a', true)
+    expect(history.state).toEqual({ index: 1, title: '房间' })
+    writeEntry('/b', true, '搜索')
+    expect(history.urls).toEqual(['/b'])
+    expect(currentEntry()).toEqual({ position: { index: 1, last: 1 }, title: '搜索' })
+  })
+
+  it('浏览器限制调用频率时地址暂时落后，序号不变，页面照常', async () => {
+    const { writeEntry, currentEntry, history } = await open()
+    history.failure = new DOMException('Too many calls', 'SecurityError')
+    expect(() => writeEntry('/a', false)).not.toThrow()
+    expect(() => writeEntry('/b', true, '甲')).not.toThrow()
+    expect(currentEntry()).toEqual({ position: { index: 0, last: 0 }, title: undefined })
+
+    history.failure = null
+    writeEntry('/c', false)
+    expect(currentEntry().position).toEqual({ index: 1, last: 1 })
+  })
+
+  it('后退到别的脚本写入的记录时，序号保持不变', async () => {
+    const { writeEntry, currentEntry, history, log } = await open()
+    writeEntry('/a', false)
+    writeEntry('/b', false)
+    history.entries[1] = { state: 'other', url: '/a' }
+    history.press()
+    expect(currentEntry().position).toEqual({ index: 2, last: 2 })
+    expect(log).toEqual(['notify'])
+  })
+
+  it('其他错误照常抛出', async () => {
+    const { writeEntry, history } = await open()
+    history.failure = new DOMException('bad', 'DataCloneError')
+    expect(() => writeEntry('/a', false)).toThrow('bad')
+  })
+})
+
+describe('弹窗', () => {
+  it('整个弹窗栈只占一条记录，标记不占序号', async () => {
+    const { registerModalHistory, currentEntry, history } = await open()
+    registerModalHistory(() => {})
+    registerModalHistory(() => {})
+    expect(history.entries).toHaveLength(2)
+    expect(history.state).toEqual({ index: 0, modal: true })
+    expect(currentEntry().position).toEqual({ index: 0, last: 0 })
+  })
+
+  it('返回键只关最上层的弹窗，下面还有弹窗时重新压入标记', async () => {
+    const { registerModalHistory, history, log } = await open()
+    registerModalHistory(() => log.push('close 1'))
+    registerModalHistory(() => log.push('close 2'))
+    history.press()
+    expect(log).toEqual(['notify', 'close 2'])
+    expect(history.state).toEqual({ index: 0, modal: true })
+
+    history.press()
+    expect(log).toEqual(['notify', 'close 2', 'notify', 'close 1'])
+    expect(history.state).toEqual({ index: 0 })
+  })
+
+  it('代码关闭弹窗时退掉标记，关闭之前再调用也不重复后退', async () => {
+    const { registerModalHistory, history, log } = await open()
+    const close = registerModalHistory(() => log.push('close'))
+    close()
+    close()
+    expect(history.traversals).toEqual([-1])
+    history.settle()
+    expect(history.state).toEqual({ index: 0 })
+    expect(log).toEqual(['notify'])
+  })
+
+  it('重复关闭同一个弹窗时不影响其他弹窗', async () => {
+    const { registerModalHistory, history, log } = await open()
+    const close = registerModalHistory(() => log.push('close 1'))
+    registerModalHistory(() => log.push('close 2'))
+    close()
+    close()
+    history.press()
+    expect(log).toEqual(['notify', 'close 2'])
+  })
+
+  it('正在退掉标记时关闭弹窗，不再后退一次', async () => {
+    const { registerModalHistory, writeEntry, history } = await open()
+    const close = registerModalHistory(() => {})
+    writeEntry('/filtered', true)
+    close()
+    expect(history.traversals).toEqual([-1])
+  })
+
+  it('后退之后打开弹窗，前面的记录就没有了', async () => {
+    const { registerModalHistory, writeEntry, currentEntry, history } = await open()
+    writeEntry('/a', false)
+    history.press()
+    expect(currentEntry().position).toEqual({ index: 0, last: 1 })
+    registerModalHistory(() => {})
+    expect(currentEntry().position).toEqual({ index: 0, last: 0 })
+  })
+
+  it('下面还有弹窗时，关闭上层的弹窗不后退', async () => {
+    const { registerModalHistory, history } = await open()
+    registerModalHistory(() => {})
+    const close = registerModalHistory(() => {})
+    close()
+    expect(history.traversals).toEqual([])
+  })
+
+  it('退掉标记期间的写入排队，落在页面的记录上', async () => {
+    const { registerModalHistory, writeEntry, currentEntry, history } = await open()
+    const close = registerModalHistory(() => {})
+    close()
+    writeEntry('/next', false, '下一页')
+    expect(history.urls).toEqual(['/start', '/start'])
+
+    history.settle()
+    expect(history.urls).toEqual(['/start', '/next'])
+    expect(currentEntry()).toEqual({ position: { index: 1, last: 1 }, title: '下一页' })
+  })
+
+  it('弹窗开着时替换地址：先退到页面的记录再替换，然后压回标记', async () => {
+    const { registerModalHistory, writeEntry, history, log } = await open()
+    registerModalHistory(() => log.push('close'))
+    writeEntry('/filtered', true)
+    writeEntry('/filtered-more', true)
+    expect(history.traversals).toEqual([-1])
+
+    history.settle()
+    expect(history.urls).toEqual(['/filtered-more', '/filtered-more'])
+    expect(history.entries.map(entry => entry.state)).toEqual([{ index: 0 }, { index: 0, modal: true }])
+    expect(log).toEqual(['notify'])
+  })
+
+  it('在弹窗里换页面时，新页面的记录顶替标记', async () => {
+    const { registerModalHistory, writeEntry, currentEntry, history } = await open()
+    registerModalHistory(() => {})
+    writeEntry('/room', false)
+    expect(history.urls).toEqual(['/start', '/room'])
+    expect(history.state).toEqual({ index: 1 })
+    expect(currentEntry().position).toEqual({ index: 1, last: 1 })
+  })
+
+  it('前进到已经关闭的弹窗留下的标记时退回页面', async () => {
+    const { registerModalHistory, history, log } = await open()
+    registerModalHistory(() => {})()
+    history.settle()
+    log.length = 0
+
+    history.press(1)
+    expect(history.traversals).toEqual([-1])
+    expect(log).toEqual([])
+    history.settle()
+    expect(history.state).toEqual({ index: 0 })
+    expect(log).toEqual(['notify'])
+  })
+
+  it('写不进标记时弹窗照常打开，返回键关掉它的同时后退一页', async () => {
+    const { registerModalHistory, writeEntry, history, log } = await open()
+    writeEntry('/a', false)
+    history.failure = new DOMException('Too many calls', 'SecurityError')
+    registerModalHistory(() => log.push('close'))
+    history.failure = null
+    expect(history.entries).toHaveLength(2)
+
+    history.press()
+    expect(history.urls[history.at]).toBe('/start')
+    expect(log).toEqual(['notify', 'close'])
+  })
+
+  it('页面先跟上记录再关弹窗：关弹窗时可能接着导航', async () => {
+    const { registerModalHistory, writeEntry, history, log } = await open()
+    registerModalHistory(() => {
+      log.push('close')
+      writeEntry('/after-close', false)
+    })
+    history.press()
+    expect(log).toEqual(['notify', 'close'])
+    expect(history.urls).toEqual(['/start', '/after-close'])
+  })
+})
+
+describe('后退一页', () => {
+  it('没有弹窗时直接后退', async () => {
+    const { goBack, writeEntry, history, log } = await open()
+    writeEntry('/a', false)
+    goBack()
+    expect(history.traversals).toEqual([-1])
+    history.settle()
+    expect(log).toEqual(['notify'])
+  })
+
+  it('标记压在页面上时只退到页面的记录，已经在退时不再后退', async () => {
+    const { goBack, registerModalHistory, history } = await open()
+    registerModalHistory(() => {})
+    goBack()
+    goBack()
+    expect(history.traversals).toEqual([-1])
+  })
+})