diff --git a/services/document-updater/test/acceptance/js/GettingADocumentTests.js b/services/document-updater/test/acceptance/js/GettingADocumentTests.js
index 02c343e38e..9da5c541ea 100644
--- a/services/document-updater/test/acceptance/js/GettingADocumentTests.js
+++ b/services/document-updater/test/acceptance/js/GettingADocumentTests.js
@@ -147,14 +147,7 @@ describe('Getting a document', function () {
 
   describe('when the web api returns an error', function () {
     before(function () {
-      sinon
-        .stub(MockWebApi, 'getDocument')
-        .callsFake((projectId, docId, callback) => {
-          if (callback == null) {
-            callback = function () {}
-          }
-          callback(new Error('oops'))
-        })
+      sinon.stub(MockWebApi, 'getDocument').rejects(new Error('oops'))
     })
 
     after(function () {
@@ -173,14 +166,11 @@ describe('Getting a document', function () {
   describe('when the web api http request takes a long time', function () {
     before(function (done) {
       this.timeout = 10000
-      sinon
-        .stub(MockWebApi, 'getDocument')
-        .callsFake((projectId, docId, callback) => {
-          if (callback == null) {
-            callback = function () {}
-          }
-          setTimeout(callback, 30000)
+      sinon.stub(MockWebApi, 'getDocument').returns(
+        new Promise(resolve => {
+          setTimeout(() => resolve(null), 30000)
         })
+      )
       done()
     })
 
diff --git a/services/document-updater/test/acceptance/js/RangesTests.js b/services/document-updater/test/acceptance/js/RangesTests.js
index 26b10f245d..fda7ca28dc 100644
--- a/services/document-updater/test/acceptance/js/RangesTests.js
+++ b/services/document-updater/test/acceptance/js/RangesTests.js
@@ -205,15 +205,7 @@ describe('Ranges', function () {
 
     it('should flush the ranges to the persistence layer again', async function () {
       await DocUpdaterClient.flushDoc(this.project_id, this.doc.id)
-      const doc = await new Promise((resolve, reject) => {
-        MockWebApi.getDocument(this.project_id, this.doc.id, (error, doc) => {
-          if (error) {
-            reject(error)
-          } else {
-            resolve(doc)
-          }
-        })
-      })
+      const doc = await MockWebApi.getDocument(this.project_id, this.doc.id)
       const { changes } = doc.ranges
       changes[0].op.should.deep.equal({ i: '123', p: 1 })
       changes[1].op.should.deep.equal({ i: '456', p: 5 })
diff --git a/services/document-updater/test/acceptance/js/helpers/MockWebApi.js b/services/document-updater/test/acceptance/js/helpers/MockWebApi.js
index 5bc3910c7b..e4625d4bd7 100644
--- a/services/document-updater/test/acceptance/js/helpers/MockWebApi.js
+++ b/services/document-updater/test/acceptance/js/helpers/MockWebApi.js
@@ -1,17 +1,7 @@
-/* eslint-disable
-    no-return-assign,
-*/
-// TODO: This file was created by bulk-decaffeinate.
-// Fix any style issues and re-enable lint.
-/*
- * decaffeinate suggestions:
- * DS102: Remove unnecessary code created because of implicit returns
- * DS207: Consider shorter variations of null checks
- * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
- */
 let MockWebApi
 const express = require('express')
 const bodyParser = require('body-parser')
+const { expressify } = require('@overleaf/promise-utils')
 const app = express()
 const MAX_REQUEST_SIZE = 2 * (2 * 1024 * 1024 + 64 * 1024)
 
@@ -33,19 +23,15 @@ module.exports = MockWebApi = {
     return (this.docs[`${projectId}:${docId}`] = doc)
   },
 
-  setDocument(
+  async setDocument(
     projectId,
     docId,
     lines,
     version,
     ranges,
     lastUpdatedAt,
-    lastUpdatedBy,
-    callback
+    lastUpdatedBy
   ) {
-    if (callback == null) {
-      callback = function () {}
-    }
     const doc =
       this.docs[`${projectId}:${docId}`] ||
       (this.docs[`${projectId}:${docId}`] = {})
@@ -55,54 +41,51 @@ module.exports = MockWebApi = {
     doc.pathname = '/a/b/c.tex'
     doc.lastUpdatedAt = lastUpdatedAt
     doc.lastUpdatedBy = lastUpdatedBy
-    return callback(null)
   },
 
-  getDocument(projectId, docId, callback) {
-    if (callback == null) {
-      callback = function () {}
-    }
-    return callback(null, this.docs[`${projectId}:${docId}`])
+  async getDocument(projectId, docId) {
+    return this.docs[`${projectId}:${docId}`]
   },
 
   run() {
-    app.get('/project/:project_id/doc/:doc_id', (req, res, next) => {
-      return this.getDocument(
-        req.params.project_id,
-        req.params.doc_id,
-        (error, doc) => {
-          if (error != null) {
-            return res.sendStatus(500)
-          } else if (doc != null) {
+    app.get(
+      '/project/:project_id/doc/:doc_id',
+      expressify(async (req, res, next) => {
+        try {
+          const doc = await this.getDocument(
+            req.params.project_id,
+            req.params.doc_id
+          )
+          if (doc != null) {
             return res.send(JSON.stringify(doc))
           } else {
             return res.sendStatus(404)
           }
+        } catch (error) {
+          return res.sendStatus(500)
         }
-      )
-    })
+      })
+    )
 
     app.post(
       '/project/:project_id/doc/:doc_id',
       bodyParser.json({ limit: MAX_REQUEST_SIZE }),
-      (req, res, next) => {
-        return MockWebApi.setDocument(
-          req.params.project_id,
-          req.params.doc_id,
-          req.body.lines,
-          req.body.version,
-          req.body.ranges,
-          req.body.lastUpdatedAt,
-          req.body.lastUpdatedBy,
-          error => {
-            if (error != null) {
-              return res.sendStatus(500)
-            } else {
-              return res.json({ rev: '123' })
-            }
-          }
-        )
-      }
+      expressify(async (req, res, next) => {
+        try {
+          await MockWebApi.setDocument(
+            req.params.project_id,
+            req.params.doc_id,
+            req.body.lines,
+            req.body.version,
+            req.body.ranges,
+            req.body.lastUpdatedAt,
+            req.body.lastUpdatedBy
+          )
+          return res.json({ rev: '123' })
+        } catch (error) {
+          return res.sendStatus(500)
+        }
+      })
     )
 
     return app