diff --git a/rollup.config.js b/rollup.config.js
index 7fce1eea..ac14611f 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -11,6 +11,9 @@ const customModules = new Set([
   'y-dom',
   'y-prosemirror'
 ])
+/**
+ * @type {Set<any>}
+ */
 const customLibModules = new Set([
   // 'funlib',
   // 'y-protocols'
diff --git a/tests/helper.js b/tests/helper.js
deleted file mode 100644
index d8235d86..00000000
--- a/tests/helper.js
+++ /dev/null
@@ -1,413 +0,0 @@
-
-import * as Y from '../src/index.js'
-import { ItemJSON } from '../src/structs/ItemJSON.js'
-import { ItemString } from '../src/structs/ItemString.js'
-import { defragmentItemContent } from '../src/utils/defragmentItemContent.js'
-import Quill from 'quill'
-import { GC } from '../src/structs/GC.js'
-import * as random from 'lib0/prng.js'
-import * as syncProtocol from 'y-protocols/sync.js'
-import * as encoding from 'lib0/encoding.js'
-import * as decoding from 'lib0/decoding.js'
-import { createMutex } from 'lib0/mutex.js'
-import { QuillBinding } from 'y-quill'
-import { DomBinding } from 'y-dom'
-
-export * from '../src/index.js'
-
-/**
- * @param {TestYInstance} y
- * @param {Y.Transaction} transaction
- */
-const afterTransaction = (y, transaction) => {
-  y.mMux(() => {
-    if (transaction.encodedStructsLen > 0) {
-      const encoder = encoding.createEncoder()
-      syncProtocol.writeUpdate(encoder, transaction.encodedStructsLen, transaction.encodedStructs)
-      broadcastMessage(y, encoding.toBuffer(encoder))
-    }
-  })
-}
-
-export class TestYInstance extends Y.Y {
-  /**
-   * @param {TestConnector} testConnector
-   */
-  constructor (testConnector, clientID) {
-    super()
-    this.userID = clientID // overwriting clientID
-    /**
-     * @type {TestConnector}
-     */
-    this.tc = testConnector
-    /**
-     * @type {Map<TestYInstance, Array<ArrayBuffer>>}
-     */
-    this.receiving = new Map()
-    /**
-     * Message mutex
-     * @type {Function}
-     */
-    this.mMux = createMutex()
-    testConnector.allConns.add(this)
-    // set up observe on local model
-    this.on('afterTransaction', afterTransaction)
-    this.connect()
-  }
-  /**
-   * Disconnect from TestConnector.
-   */
-  disconnect () {
-    this.receiving = new Map()
-    this.tc.onlineConns.delete(this)
-  }
-  /**
-   * Append yourself to the list of known Y instances in testconnector.
-   * Also initiate sync with all clients.
-   */
-  connect () {
-    if (!this.tc.onlineConns.has(this)) {
-      this.tc.onlineConns.add(this)
-      const encoder = encoding.createEncoder()
-      syncProtocol.writeSyncStep1(encoder, this)
-      // publish SyncStep1
-      broadcastMessage(this, encoding.toBuffer(encoder))
-      this.tc.onlineConns.forEach(remoteYInstance => {
-        if (remoteYInstance !== this) {
-          // remote instance sends instance to this instance
-          const encoder = encoding.createEncoder()
-          syncProtocol.writeSyncStep1(encoder, remoteYInstance)
-          this._receive(encoding.toBuffer(encoder), remoteYInstance)
-        }
-      })
-    }
-  }
-  /**
-   * Receive a message from another client. This message is only appended to the list of receiving messages.
-   * TestConnector decides when this client actually reads this message.
-   *
-   * @param {ArrayBuffer} message
-   * @param {TestYInstance} remoteClient
-   */
-  _receive (message, remoteClient) {
-    let messages = this.receiving.get(remoteClient)
-    if (messages === undefined) {
-      messages = []
-      this.receiving.set(remoteClient, messages)
-    }
-    messages.push(message)
-  }
-}
-
-/**
- * Keeps track of TestYInstances.
- *
- * The TestYInstances add/remove themselves from the list of connections maintained in this object.
- * I think it makes sense. Deal with it.
- */
-export class TestConnector {
-  constructor (prng) {
-    /**
-     * @type {Set<TestYInstance>}
-     */
-    this.allConns = new Set()
-    /**
-     * @type {Set<TestYInstance>}
-     */
-    this.onlineConns = new Set()
-    /**
-     * @type {random.PRNG}
-     */
-    this.prng = prng
-  }
-  /**
-   * Create a new Y instance and add it to the list of connections
-   * @param {number} clientID
-   */
-  createY (clientID) {
-    return new TestYInstance(this, clientID)
-  }
-  /**
-   * Choose random connection and flush a random message from a random sender.
-   *
-   * If this function was unable to flush a message, because there are no more messages to flush, it returns false. true otherwise.
-   * @return {boolean}
-   */
-  flushRandomMessage () {
-    const prng = this.prng
-    const conns = Array.from(this.onlineConns).filter(conn => conn.receiving.size > 0)
-    if (conns.length > 0) {
-      const receiver = random.oneOf(prng, conns)
-      const [sender, messages] = random.oneOf(prng, Array.from(receiver.receiving))
-      const m = messages.shift()
-      if (messages.length === 0) {
-        receiver.receiving.delete(sender)
-      }
-      const encoder = encoding.createEncoder()
-      receiver.mMux(() => {
-        // console.log('receive (' + sender.userID + '->' + receiver.userID + '):\n', syncProtocol.stringifySyncMessage(decoding.createDecoder(m), receiver))
-        // do not publish data created when this function is executed (could be ss2 or update message)
-        syncProtocol.readSyncMessage(decoding.createDecoder(m), encoder, receiver)
-      })
-      if (encoding.length(encoder) > 0) {
-        // send reply message
-        sender._receive(encoding.toBuffer(encoder), receiver)
-      }
-      return true
-    }
-    return false
-  }
-  /**
-   * @return {boolean} True iff this function actually flushed something
-   */
-  flushAllMessages () {
-    let didSomething = false
-    while (this.flushRandomMessage()) {
-      didSomething = true
-    }
-    return didSomething
-  }
-  reconnectAll () {
-    this.allConns.forEach(conn => conn.connect())
-  }
-  disconnectAll () {
-    this.allConns.forEach(conn => conn.disconnect())
-  }
-  syncAll () {
-    this.reconnectAll()
-    this.flushAllMessages()
-  }
-  /**
-   * @return {boolean} Whether it was possible to disconnect a randon connection.
-   */
-  disconnectRandom () {
-    if (this.onlineConns.size === 0) {
-      return false
-    }
-    random.oneOf(this.prng, Array.from(this.onlineConns)).disconnect()
-    return true
-  }
-  /**
-   * @return {boolean} Whether it was possible to reconnect a random connection.
-   */
-  reconnectRandom () {
-    const reconnectable = []
-    this.allConns.forEach(conn => {
-      if (!this.onlineConns.has(conn)) {
-        reconnectable.push(conn)
-      }
-    })
-    if (reconnectable.length === 0) {
-      return false
-    }
-    random.oneOf(this.prng, reconnectable).connect()
-    return true
-  }
-}
-
-/**
- * @param {TestYInstance} y // publish message created by `y` to all other online clients
- * @param {ArrayBuffer} m
- */
-const broadcastMessage = (y, m) => {
-  if (y.tc.onlineConns.has(y)) {
-    y.tc.onlineConns.forEach(remoteYInstance => {
-      if (remoteYInstance !== y) {
-        remoteYInstance._receive(m, y)
-      }
-    })
-  }
-}
-
-/**
- * Convert DS to a proper DeleteSet of Map.
- *
- * @param {Y.Y} y
- * @return {Object<number, Array<[number, number, boolean]>>}
- */
-const getDeleteSet = y => {
-  /**
-   * @type {Object<number, Array<[number, number, boolean]>}
-   */
-  var ds = {}
-  y.ds.iterate(null, null, n => {
-    var user = n._id.user
-    var counter = n._id.clock
-    var len = n.len
-    var gc = n.gc
-    var dv = ds[user]
-    if (dv === void 0) {
-      dv = []
-      ds[user] = dv
-    }
-    dv.push([counter, len, gc])
-  })
-  return ds
-}
-
-/**
- * 1. reconnect and flush all
- * 2. user 0 gc
- * 3. get type content
- * 4. disconnect & reconnect all (so gc is propagated)
- * 5. compare os, ds, ss
- *
- * @param {any} t
- * @param {Array<TestYInstance>} users
- */
-export const compareUsers = (t, users) => {
-  users.forEach(u => u.connect())
-  do {
-    users.forEach(u => {
-      // flush dom changes
-      u.domBinding._beforeTransactionHandler(null, null, false)
-    })
-  } while (users[0].tc.flushAllMessages())
-
-  var userArrayValues = users.map(u => u.define('array', Y.Array).toJSON().map(val => JSON.stringify(val)))
-  var userMapValues = users.map(u => u.define('map', Y.Map).toJSON())
-  var userXmlValues = users.map(u => u.define('xml', Y.XmlElement).toString())
-  var userTextValues = users.map(u => u.define('text', Y.Text).toDelta())
-  var userQuillValues = users.map(u => {
-    u.quill.update('yjs') // get latest changes
-    return u.quill.getContents().ops
-  })
-
-  var data = users.map(u => {
-    defragmentItemContent(u)
-    var data = {}
-    let ops = []
-    u.os.iterate(null, null, op => {
-      let json
-      if (op.constructor === GC) {
-        json = {
-          type: 'GC',
-          id: op._id,
-          length: op._length,
-          content: null
-        }
-      } else {
-        json = {
-          id: op._id,
-          left: op._left === null ? null : op._left._lastId,
-          right: op._right === null ? null : op._right._id,
-          length: op._length,
-          deleted: op._deleted,
-          parent: op._parent._id,
-          content: null
-        }
-      }
-      if (op instanceof ItemJSON || op instanceof ItemString) {
-        json.content = op._content
-      }
-      ops.push(json)
-    })
-    data.os = ops
-    data.ds = getDeleteSet(u)
-    const ss = {}
-    u.ss.state.forEach((clock, user) => {
-      ss[user] = clock
-    })
-    data.ss = ss
-    return data
-  })
-  for (var i = 0; i < data.length - 1; i++) {
-    t.group(() => {
-      t.compare(userArrayValues[i].length, users[i].get('array').length, 'array length correctly computed')
-      t.compare(userArrayValues[i], userArrayValues[i + 1], 'array types')
-      t.compare(userMapValues[i], userMapValues[i + 1], 'map types')
-      t.compare(userXmlValues[i], userXmlValues[i + 1], 'xml types')
-      t.compare(userTextValues[i].map(a => a.insert).join('').length, users[i].get('text').length, 'text length correctly computed')
-      t.compare(userTextValues[i], userTextValues[i + 1], 'text types')
-      t.compare(userQuillValues[i], userQuillValues[i + 1], 'quill delta content')
-      t.compare(data[i].os, data[i + 1].os, 'os')
-      t.compare(data[i].ds, data[i + 1].ds, 'ds')
-      t.compare(data[i].ss, data[i + 1].ss, 'ss')
-    }, `Compare user${i} with user${i + 1}`)
-  }
-  users.forEach(user => {
-    if (user._missingStructs.size !== 0) {
-      t.fail('missing structs should mes empty!')
-    }
-  })
-  users.map(u => u.destroy())
-}
-
-/**
- * @param {string} nodeName
- * @param {Map<string, string>} attrs
- * @return {null|Map<string, string>}
- */
-const filter = (nodeName, attrs) => {
-  if (nodeName === 'HIDDEN') {
-    return null
-  }
-  attrs.delete('hidden')
-  return attrs
-}
-
-/**
- * @param {any} t
- * @param {any} opts
- * @return {any}
- */
-export const initArrays = (t, opts) => {
-  var result = {
-    users: []
-  }
-  var prng = opts.prng || random.createPRNG(t.getSeed())
-  const testConnector = new TestConnector(prng)
-  result.testConnector = testConnector
-  for (let i = 0; i < opts.users; i++) {
-    let y = testConnector.createY(i)
-    result.users.push(y)
-    result['array' + i] = y.define('array', Y.Array)
-    result['map' + i] = y.define('map', Y.Map)
-    const yxml = y.define('xml', Y.XmlElement)
-    result['xml' + i] = yxml
-    const dom = document.createElement('my-dom')
-    const domBinding = new DomBinding(yxml, dom, { filter })
-    result['domBinding' + i] = domBinding
-    result['dom' + i] = dom
-    const textType = y.define('text', Y.Text)
-    result['text' + i] = textType
-    const quill = new Quill(document.createElement('div'))
-    result['quillBinding' + i] = new QuillBinding(textType, quill)
-    result['quill' + i] = quill
-    y.quill = quill // put quill on the y object (so we can use it later)
-    y.dom = dom
-    y.domBinding = domBinding
-  }
-  testConnector.syncAll()
-  return result
-}
-
-export const applyRandomTests = (t, mods, iterations) => {
-  const prng = random.createPRNG(t.getSeed())
-  const result = initArrays(t, { users: 5, prng })
-  const { testConnector, users } = result
-  for (var i = 0; i < iterations; i++) {
-    if (random.int32(prng, 0, 100) <= 2) {
-      // 2% chance to disconnect/reconnect a random user
-      if (random.bool(prng)) {
-        testConnector.disconnectRandom()
-      } else {
-        testConnector.reconnectRandom()
-      }
-    } else if (random.int32(prng, 0, 100) <= 1) {
-      // 1% chance to flush all & garbagecollect
-      // TODO: We do not gc all users as this does not work yet
-      // await garbageCollectUsers(t, users)
-      testConnector.flushAllMessages()
-      // await users[0].db.emptyGarbageCollector() // TODO: reintroduce GC tests!
-    } else if (random.int32(prng, 0, 100) <= 50) {
-      // 50% chance to flush a random message
-      testConnector.flushRandomMessage()
-    }
-    let user = random.oneOf(prng, users)
-    var test = random.oneOf(prng, mods)
-    test(t, user, prng)
-  }
-  compareUsers(t, users)
-  return result
-}
diff --git a/tests/index.html b/tests/index.html
deleted file mode 100644
index cf894761..00000000
--- a/tests/index.html
+++ /dev/null
@@ -1,8 +0,0 @@
-<!DOCTYPE html>
-<html>
-  <head>
-  </head>
-  <body>
-    <script type="module" src="./DeleteStore.tests.js"></script>
-  </body>
-</html>
diff --git a/tests/index.js b/tests/index.js
index a215a975..bb332e3f 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -6,8 +6,9 @@ import * as deleteStore from './DeleteStore.tests.js'
 import * as array from './y-array.tests.js'
 import * as map from './y-map.tests.js'
 import * as text from './y-text.tests.js'
+import * as xml from './y-xml.tests.js'
 
 if (isBrowser) {
   log.createVConsole(document.body)
 }
-runTests({ deleteStore, map, array, text })
+runTests({ deleteStore, map, array, text, xml })
diff --git a/tests/y-xml.tests.js b/tests/y-xml.tests.js
index f7e0a06b..d3ea9d28 100644
--- a/tests/y-xml.tests.js
+++ b/tests/y-xml.tests.js
@@ -1,20 +1,20 @@
-import { initArrays, compareUsers } from './helper.js'
-import { test } from 'cutest'
+import { init, compare } from './testHelper.js'
 import * as Y from '../src/index.js'
+import * as t from 'lib0/testing.js'
 
-test('set property', async function xml0 (t) {
-  var { testConnector, users, xml0, xml1 } = await initArrays(t, { users: 2 })
+export const testSetProperty = tc => {
+  const { testConnector, users, xml0, xml1 } = init(tc, { users: 2 })
   xml0.setAttribute('height', '10')
   t.assert(xml0.getAttribute('height') === '10', 'Simple set+get works')
   testConnector.flushAllMessages()
   t.assert(xml1.getAttribute('height') === '10', 'Simple set+get works (remote)')
-  await compareUsers(t, users)
-})
+  compare(users)
+}
 
-test('events', async function xml1 (t) {
-  var { testConnector, users, xml0, xml1 } = await initArrays(t, { users: 2 })
-  var event = { attributesChanged: new Set() }
-  var remoteEvent = { attributesChanged: new Set() }
+export const testEvents = tc => {
+  const { testConnector, users, xml0, xml1 } = init(tc, { users: 2 })
+  let event = { attributesChanged: new Set() }
+  let remoteEvent = { attributesChanged: new Set() }
   xml0.observe(e => {
     delete e._content
     delete e.nodes
@@ -45,96 +45,11 @@ test('events', async function xml1 (t) {
   t.assert(event.childListChanged, 'YXmlEvent.childListChanged on deleted element')
   testConnector.flushAllMessages()
   t.assert(remoteEvent.childListChanged, 'YXmlEvent.childListChanged on deleted element (remote)')
-  await compareUsers(t, users)
-})
+  compare(users)
+}
 
-test('attribute modifications (y -> dom)', async function xml2 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.setAttribute('height', '100px')
-  t.assert(dom0.getAttribute('height') === '100px', 'setAttribute')
-  xml0.removeAttribute('height')
-  t.assert(dom0.getAttribute('height') == null, 'removeAttribute')
-  xml0.setAttribute('class', 'stuffy stuff')
-  t.assert(dom0.getAttribute('class') === 'stuffy stuff', 'set class attribute')
-  await compareUsers(t, users)
-})
-
-test('element insert (y -> dom)', async function xml5 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlText('some text')])
-  xml0.insert(1, [new Y.XmlElement('p')])
-  t.assert(dom0.childNodes[0].textContent === 'some text', 'Retrieve Text node')
-  t.assert(dom0.childNodes[1].nodeName === 'P', 'Retrieve Element node')
-  await compareUsers(t, users)
-})
-
-test('y on insert, then delete (y -> dom)', async function xml7 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlElement('p')])
-  t.assert(dom0.childNodes[0].nodeName === 'P', 'Get inserted element from dom')
-  xml0.delete(0, 1)
-  t.assert(dom0.childNodes.length === 0, '#childNodes is empty after delete')
-  await compareUsers(t, users)
-})
-
-test('delete consecutive (1) (Text)', async function xml8 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlText('1'), new Y.XmlText('2'), new Y.XmlText('3')])
-  xml0.delete(1, 2)
-  t.assert(xml0.length === 1, 'check length (y)')
-  t.assert(dom0.childNodes.length === 1, 'check length (dom)')
-  t.assert(dom0.childNodes[0].textContent === '1', 'check content')
-  await compareUsers(t, users)
-})
-
-test('delete consecutive (2) (Text)', async function xml9 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlText('1'), new Y.XmlText('2'), new Y.XmlText('3')])
-  xml0.delete(0, 1)
-  xml0.delete(1, 1)
-  t.assert(xml0.length === 1, 'check length (y)')
-  t.assert(dom0.childNodes.length === 1, 'check length (dom)')
-  t.assert(dom0.childNodes[0].textContent === '2', 'check content')
-  await compareUsers(t, users)
-})
-
-test('delete consecutive (1) (Element)', async function xml10 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlElement('A'), new Y.XmlElement('B'), new Y.XmlElement('C')])
-  xml0.delete(1, 2)
-  t.assert(xml0.length === 1, 'check length (y)')
-  t.assert(dom0.childNodes.length === 1, 'check length (dom)')
-  t.assert(dom0.childNodes[0].nodeName === 'A', 'check content')
-  await compareUsers(t, users)
-})
-
-test('delete consecutive (2) (Element)', async function xml11 (t) {
-  var { users, xml0, dom0 } = await initArrays(t, { users: 3 })
-  xml0.insert(0, [new Y.XmlElement('A'), new Y.XmlElement('B'), new Y.XmlElement('C')])
-  xml0.delete(0, 1)
-  xml0.delete(1, 1)
-  t.assert(xml0.length === 1, 'check length (y)')
-  t.assert(dom0.childNodes.length === 1, 'check length (dom)')
-  t.assert(dom0.childNodes[0].nodeName === 'B', 'check content')
-  await compareUsers(t, users)
-})
-
-test('Receive a bunch of elements (with disconnect)', async function xml12 (t) {
-  var { testConnector, users, xml0, xml1, dom0, dom1 } = await initArrays(t, { users: 3 })
-  users[1].disconnect()
-  xml0.insert(0, [new Y.XmlElement('A'), new Y.XmlElement('B'), new Y.XmlElement('C')])
-  xml0.insert(0, [new Y.XmlElement('X'), new Y.XmlElement('Y'), new Y.XmlElement('Z')])
-  await users[1].connect()
-  testConnector.flushAllMessages()
-  t.assert(xml0.length === 6, 'check length (y)')
-  t.assert(xml1.length === 6, 'check length (y) (reconnected user)')
-  t.assert(dom0.childNodes.length === 6, 'check length (dom)')
-  t.assert(dom1.childNodes.length === 6, 'check length (dom) (reconnected user)')
-  await compareUsers(t, users)
-})
-
-test('treeWalker', async function xml17 (t) {
-  var { users, xml0 } = await initArrays(t, { users: 3 })
+export const testTreewalker = tc => {
+  const { users, xml0 } = init(tc, { users: 3 })
   let paragraph1 = new Y.XmlElement('p')
   let paragraph2 = new Y.XmlElement('p')
   let text1 = new Y.XmlText('init')
@@ -146,5 +61,5 @@ test('treeWalker', async function xml17 (t) {
   t.assert(allParagraphs[0] === paragraph1, 'querySelectorAll found paragraph1')
   t.assert(allParagraphs[1] === paragraph2, 'querySelectorAll found paragraph2')
   t.assert(xml0.querySelector('p') === paragraph1, 'querySelector found paragraph1')
-  await compareUsers(t, users)
-})
+  compare(users)
+}