diff --git a/package-lock.json b/package-lock.json
index c7b9e4d..a42045e 100644
--- a/package-lock.json
+++ b/package-lock.json
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-          "integrity": "sha1-GSa6kM8+3+KttJJ/WIC8IsZseQ8=",
+          "version": "1.10.5",
+          "resolved": "https://registry.npmjs.org/growl/-/growl-1.10.5.tgz",
+          "integrity": "sha512-qBr4OuELkhPenW6goKVXiv47US3clb3/IbuWF9KNKEijAy9oeHxU9IgzjvJhHkUzhaj7rOUD7+YGWqUjLp5oSA==",
           "dev": true
         },
+        "locate-path": {
+          "version": "3.0.0",
+          "resolved": "https://registry.npmjs.org/locate-path/-/locate-path-3.0.0.tgz",
+          "integrity": "sha512-7AO748wWnIhNqAuaty2ZWHkQHRSNfPVIsPIfwEOWO22AmaoVrWavlOcMR5nzTLNYvp36X220/maaRsrec1G65A==",
+          "dev": true,
+          "requires": {
+            "p-locate": "^3.0.0",
+            "path-exists": "^3.0.0"
+          }
+        },
         "mkdirp": {
           "version": "0.5.1",
           "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.1.tgz",
@@ -4020,6 +4187,21 @@
           "requires": {
             "minimist": "0.0.8"
           }
+        },
+        "ms": {
+          "version": "2.1.1",
+          "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.1.tgz",
+          "integrity": "sha512-tgp+dl5cGk28utYktBsrFqA7HKgrhgPsg6Z/EfhWI4gl1Hwq8B/GmY/0oXZ6nF8hDVesS/FpnYaD/kOWhYQvyg==",
+          "dev": true
+        },
+        "p-locate": {
+          "version": "3.0.0",
+          "resolved": "https://registry.npmjs.org/p-locate/-/p-locate-3.0.0.tgz",
+          "integrity": "sha512-x+12w/To+4GFfgJhBEpiDcLozRJGegY+Ei7/z0tSLkMmxGZNybVMSfWj9aJn8Z5Fc7dBUNJOOVgPv2H7IwulSQ==",
+          "dev": true,
+          "requires": {
+            "p-limit": "^2.0.0"
+          }
         }
       }
     },
@@ -4166,6 +4348,54 @@
       "integrity": "sha512-1nh45deeb5olNY7eX82BkPO7SSxR5SSYJiPTrTdFUVYwAl8CKMA5N9PjTYkHiRjisVcxcQ1HXdLhx2qxxJzLNQ==",
       "dev": true
     },
+    "nise": {
+      "version": "4.0.3",
+      "resolved": "https://registry.npmjs.org/nise/-/nise-4.0.3.tgz",
+      "integrity": "sha512-EGlhjm7/4KvmmE6B/UFsKh7eHykRl9VH+au8dduHLCyWUO/hr7+N+WtTvDUwc9zHuM1IaIJs/0lQ6Ag1jDkQSg==",
+      "dev": true,
+      "requires": {
+        "@sinonjs/commons": "^1.7.0",
+        "@sinonjs/fake-timers": "^6.0.0",
+        "@sinonjs/text-encoding": "^0.7.1",
+        "just-extend": "^4.0.2",
+        "path-to-regexp": "^1.7.0"
+      },
+      "dependencies": {
+        "isarray": {
+          "version": "0.0.1",
+          "resolved": "https://registry.npmjs.org/isarray/-/isarray-0.0.1.tgz",
+          "integrity": "sha1-ihis/Kmo9Bd+Cav8YDiTmwXR7t8=",
+          "dev": true
+        },
+        "path-to-regexp": {
+          "version": "1.8.0",
+          "resolved": "https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-1.8.0.tgz",
+          "integrity": "sha512-n43JRhlUKUAlibEJhPeir1ncUID16QnEjNpwzNdO3Lm4ywrBpBZ5oLD0I6br9evr1Y9JTqwRtAh7JLoOzAQdVA==",
+          "dev": true,
+          "requires": {
+            "isarray": "0.0.1"
+          }
+        }
+      }
+    },
+    "node-environment-flags": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/node-environment-flags/-/node-environment-flags-1.0.6.tgz",
+      "integrity": "sha512-5Evy2epuL+6TM0lCQGpFIj6KwiEsGh1SrHUhTbNX+sLbBtjidPZFAnVK9y5yU1+h//RitLbRHTIMyxQPtxMdHw==",
+      "dev": true,
+      "requires": {
+        "object.getownpropertydescriptors": "^2.0.3",
+        "semver": "^5.7.0"
+      },
+      "dependencies": {
+        "semver": {
+          "version": "5.7.1",
+          "resolved": "https://registry.npmjs.org/semver/-/semver-5.7.1.tgz",
+          "integrity": "sha512-sauaDf/PZdVgrLTNYHRtpXa1iRiKcaebiKQ1BJdpQlWH2lCvexQdX55snPFyK7QzpudqbCI0qXFfOasHdyNDGQ==",
+          "dev": true
+        }
+      }
+    },
     "node-fetch": {
       "version": "2.6.0",
       "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-2.6.0.tgz",
@@ -4224,6 +4454,12 @@
         "validate-npm-package-license": "^3.0.1"
       }
     },
+    "normalize-path": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/normalize-path/-/normalize-path-3.0.0.tgz",
+      "integrity": "sha512-6eZs5Ls3WtCisHWp9S2GUy8dqkpGi4BVSz3GaqiE6ezub0512ESztXUwUB6C6IKbQkY2Pnb/mD4WYojCRwcwLA==",
+      "dev": true
+    },
     "npm-bundled": {
       "version": "1.0.5",
       "resolved": "https://registry.npmjs.org/npm-bundled/-/npm-bundled-1.0.5.tgz",
@@ -4312,6 +4548,16 @@
         "has": "^1.0.3"
       }
     },
+    "object.getownpropertydescriptors": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/object.getownpropertydescriptors/-/object.getownpropertydescriptors-2.1.0.tgz",
+      "integrity": "sha512-Z53Oah9A3TdLoblT7VKJaTDdXdT+lQO+cNpKVnya5JDe9uLvzu1YyY1yFDFrcxrlRgWrEFH0jJtD/IbuwjcEVg==",
+      "dev": true,
+      "requires": {
+        "define-properties": "^1.1.3",
+        "es-abstract": "^1.17.0-next.1"
+      }
+    },
     "object.values": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/object.values/-/object.values-1.1.1.tgz",
@@ -4509,6 +4755,12 @@
       "resolved": "https://registry.npmjs.org/performance-now/-/performance-now-2.1.0.tgz",
       "integrity": "sha1-Ywn04OX6kT7BxpMHrjZLSzd8nns="
     },
+    "picomatch": {
+      "version": "2.2.1",
+      "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-2.2.1.tgz",
+      "integrity": "sha512-ISBaA8xQNmwELC7eOjqFKMESB2VIqt4PPDD0nsS95b/9dZXvVKOlz9keMSnoGGKcOHXfTvDD6WMaRoSc9UuhRA==",
+      "dev": true
+    },
     "pify": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/pify/-/pify-4.0.1.tgz",
@@ -5403,6 +5655,15 @@
         "util-deprecate": "~1.0.1"
       }
     },
+    "readdirp": {
+      "version": "3.2.0",
+      "resolved": "https://registry.npmjs.org/readdirp/-/readdirp-3.2.0.tgz",
+      "integrity": "sha512-crk4Qu3pmXwgxdSgGhgA/eXiJAPQiX4GMOZZMXnqKxHX7TaoL+3gQVo/WeuAiogr07DpnfjIMpXXa+PAIvwPGQ==",
+      "dev": true,
+      "requires": {
+        "picomatch": "^2.0.4"
+      }
+    },
     "regenerator-runtime": {
       "version": "0.13.3",
       "resolved": "https://registry.npmjs.org/regenerator-runtime/-/regenerator-runtime-0.13.3.tgz",
@@ -5784,12 +6045,41 @@
       "integrity": "sha1-tf3AjxKH6hF4Yo5BXiUTK3NkbG0="
     },
     "sinon": {
-      "version": "1.7.3",
-      "resolved": "https://registry.npmjs.org/sinon/-/sinon-1.7.3.tgz",
-      "integrity": "sha1-emnWnNApRYbHQyVO7/G1g6UJl/I=",
+      "version": "9.0.1",
+      "resolved": "https://registry.npmjs.org/sinon/-/sinon-9.0.1.tgz",
+      "integrity": "sha512-iTTyiQo5T94jrOx7X7QLBZyucUJ2WvL9J13+96HMfm2CGoJYbIPqRfl6wgNcqmzk0DI28jeGx5bUTXizkrqBmg==",
       "dev": true,
       "requires": {
-        "buster-format": "~0.5"
+        "@sinonjs/commons": "^1.7.0",
+        "@sinonjs/fake-timers": "^6.0.0",
+        "@sinonjs/formatio": "^5.0.1",
+        "@sinonjs/samsam": "^5.0.3",
+        "diff": "^4.0.2",
+        "nise": "^4.0.1",
+        "supports-color": "^7.1.0"
+      },
+      "dependencies": {
+        "diff": {
+          "version": "4.0.2",
+          "resolved": "https://registry.npmjs.org/diff/-/diff-4.0.2.tgz",
+          "integrity": "sha512-58lmxKSA4BNyLz+HHMUzlOEpg09FV+ev6ZMe3vJihgdxzgcwZ8VoEEPmALCZG9LmqfVoNMMKpttIYTVG6uDY7A==",
+          "dev": true
+        },
+        "has-flag": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz",
+          "integrity": "sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==",
+          "dev": true
+        },
+        "supports-color": {
+          "version": "7.1.0",
+          "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-7.1.0.tgz",
+          "integrity": "sha512-oRSIpR8pxT1Wr2FquTNnGet79b3BWljqOuoW/h4oBhxJ/HUbX5nX6JSruTkvXDCFMwDPvsaTTbvMLKZWSy0R5g==",
+          "dev": true,
+          "requires": {
+            "has-flag": "^4.0.0"
+          }
+        }
       }
     },
     "slice-ansi": {
@@ -6101,12 +6391,12 @@
       "integrity": "sha1-6NK6H6nJBXAwPAMLaQD31fiavls="
     },
     "supports-color": {
-      "version": "4.4.0",
-      "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-4.4.0.tgz",
-      "integrity": "sha1-iD992rwWUUKyphQn8zUt7RldGj4=",
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-6.0.0.tgz",
+      "integrity": "sha512-on9Kwidc1IUQo+bQdhi8+Tijpo0e1SS6RoGo2guUwn5vdaxw8RXOF9Vb2ws+ihWOmh4JnCJOvaziZWP1VABaLg==",
       "dev": true,
       "requires": {
-        "has-flag": "^2.0.0"
+        "has-flag": "^3.0.0"
       }
     },
     "table": {
@@ -6336,6 +6626,15 @@
       "resolved": "https://registry.npmjs.org/to-no-case/-/to-no-case-1.0.2.tgz",
       "integrity": "sha1-xyKQcWTvaxeBMsjmmTAhLRtKoWo="
     },
+    "to-regex-range": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/to-regex-range/-/to-regex-range-5.0.1.tgz",
+      "integrity": "sha512-65P7iz6X5yEr1cwcgvQxbbIw7Uk3gOy5dIdtZ4rDveLqhrdJP+Li/Hx6tyK0NEb+2GCyneCMJiGqrADCSNk8sQ==",
+      "dev": true,
+      "requires": {
+        "is-number": "^7.0.0"
+      }
+    },
     "to-snake-case": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/to-snake-case/-/to-snake-case-1.0.0.tgz",
@@ -6865,6 +7164,17 @@
         "decamelize": "^1.2.0"
       }
     },
+    "yargs-unparser": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/yargs-unparser/-/yargs-unparser-1.6.0.tgz",
+      "integrity": "sha512-W9tKgmSn0DpSatfri0nx52Joq5hVXgeLiqR/5G0sZNDoLZFOr/xjBUDcShCOGNsBnEMNo1KAMBkTej1Hm62HTw==",
+      "dev": true,
+      "requires": {
+        "flat": "^4.1.0",
+        "lodash": "^4.17.15",
+        "yargs": "^13.3.0"
+      }
+    },
     "yn": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/yn/-/yn-3.1.1.tgz",
diff --git a/package.json b/package.json
index 7317cae..bdbbd5f 100644
--- a/package.json
+++ b/package.json
@@ -58,11 +58,11 @@
     "eslint-plugin-promise": "^4.2.1",
     "eslint-plugin-react": "^7.19.0",
     "eslint-plugin-standard": "^4.0.1",
-    "mocha": "^4.0.1",
+    "mocha": "^7.1.0",
     "prettier": "^1.19.1",
     "prettier-eslint-cli": "^5.0.0",
     "sandboxed-module": "~0.3.0",
-    "sinon": "~1.7.3",
+    "sinon": "~9.0.1",
     "timekeeper": "2.2.0"
   }
 }
diff --git a/test/unit/js/CompileManagerTests.js b/test/unit/js/CompileManagerTests.js
index ae50bcc..180f6f3 100644
--- a/test/unit/js/CompileManagerTests.js
+++ b/test/unit/js/CompileManagerTests.js
@@ -347,10 +347,10 @@ describe('CompileManager', function() {
           .should.equal(true)
       })
 
-      return it('should call the callback with an error from the stderr', function() {
-        this.callback.calledWith(new Error()).should.equal(true)
+      it('should call the callback with an error from the stderr', function() {
+        this.callback.calledWithExactly(sinon.match(Error)).should.equal(true)
 
-        return this.callback.args[0][0].message.should.equal(
+        this.callback.args[0][0].message.should.equal(
           `rm -r ${this.Settings.path.compilesDir}/${this.project_id}-${this.user_id} failed: ${this.error}`
         )
       })
diff --git a/test/unit/js/DockerRunnerTests.js b/test/unit/js/DockerRunnerTests.js
index d17d906..eea66b1 100644
--- a/test/unit/js/DockerRunnerTests.js
+++ b/test/unit/js/DockerRunnerTests.js
@@ -464,8 +464,8 @@ describe('DockerRunner', function() {
         return this.createContainer.called.should.equal(false)
       })
 
-      return it('should call the callback with an error', function() {
-        return this.callback.calledWith(new Error()).should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
       })
     })
 
@@ -488,8 +488,8 @@ describe('DockerRunner', function() {
         return this.createContainer.called.should.equal(false)
       })
 
-      return it('should call the callback with an error', function() {
-        return this.callback.calledWith(new Error()).should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
       })
     })
 
@@ -582,10 +582,12 @@ describe('DockerRunner', function() {
         return this.container.kill.called.should.equal(true)
       })
 
-      return it('should call the callback with an error', function() {
-        const error = new Error('container timed out')
-        error.timedout = true
-        return this.callback.calledWith(error).should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const errorObj = this.callback.args[0][0]
+        expect(errorObj.message).to.include('container timed out')
+        expect(errorObj.timedout).equal(true)
       })
     })
   })
diff --git a/test/unit/js/LockManagerTests.js b/test/unit/js/LockManagerTests.js
index ea6c341..cb8ab9b 100644
--- a/test/unit/js/LockManagerTests.js
+++ b/test/unit/js/LockManagerTests.js
@@ -84,9 +84,10 @@ describe('DockerLockManager', function() {
         return this.runner.called.should.equal(false)
       })
 
-      return it('should return an error', function() {
-        const error = new Errors.AlreadyCompilingError()
-        return this.callback.calledWithExactly(error).should.equal(true)
+      it('should return an error', function() {
+        this.callback
+          .calledWithExactly(sinon.match(Errors.AlreadyCompilingError))
+          .should.equal(true)
       })
     })
   })
diff --git a/test/unit/js/ResourceStateManagerTests.js b/test/unit/js/ResourceStateManagerTests.js
index c0e89ef..4c16ed1 100644
--- a/test/unit/js/ResourceStateManagerTests.js
+++ b/test/unit/js/ResourceStateManagerTests.js
@@ -11,6 +11,7 @@
  */
 const SandboxedModule = require('sandboxed-module')
 const sinon = require('sinon')
+const { expect } = require('chai')
 const should = require('chai').should()
 const modulePath = require('path').join(
   __dirname,
@@ -132,11 +133,13 @@ describe('ResourceStateManager', function() {
         )
       })
 
-      return it('should call the callback with an error', function() {
-        const error = new Errors.FilesOutOfSyncError(
-          'invalid state for incremental update'
-        )
-        return this.callback.calledWith(error).should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback
+          .calledWith(sinon.match(Errors.FilesOutOfSyncError))
+          .should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('invalid state for incremental update')
       })
     })
   })
@@ -174,11 +177,15 @@ describe('ResourceStateManager', function() {
         )
       })
 
-      return it('should call the callback with an error', function() {
-        const error = new Errors.FilesOutOfSyncError(
+      it('should call the callback with an error', function() {
+        this.callback
+          .calledWith(sinon.match(Errors.FilesOutOfSyncError))
+          .should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include(
           'resource files missing in incremental update'
         )
-        return this.callback.calledWith(error).should.equal(true)
       })
     })
 
@@ -198,10 +205,11 @@ describe('ResourceStateManager', function() {
         )
       })
 
-      return it('should call the callback with an error', function() {
-        return this.callback
-          .calledWith(new Error('relative path in resource file list'))
-          .should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('relative path in resource file list')
       })
     })
   })
diff --git a/test/unit/js/ResourceWriterTests.js b/test/unit/js/ResourceWriterTests.js
index b542f25..2844ce7 100644
--- a/test/unit/js/ResourceWriterTests.js
+++ b/test/unit/js/ResourceWriterTests.js
@@ -12,6 +12,7 @@
  */
 const SandboxedModule = require('sandboxed-module')
 const sinon = require('sinon')
+const { expect } = require('chai')
 const should = require('chai').should()
 const modulePath = require('path').join(
   __dirname,
@@ -447,10 +448,11 @@ describe('ResourceWriter', function() {
         return this.fs.writeFile.called.should.equal(false)
       })
 
-      return it('should return an error', function() {
-        return this.callback
-          .calledWith(new Error('resource path is outside root directory'))
-          .should.equal(true)
+      it('should return an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('resource path is outside root directory')
       })
     })
   })
@@ -468,21 +470,18 @@ describe('ResourceWriter', function() {
 
     describe('with an invalid path', function() {
       beforeEach(function() {
-        return this.ResourceWriter.checkPath(
-          'foo',
-          'baz/../../bar',
-          this.callback
-        )
+        this.ResourceWriter.checkPath('foo', 'baz/../../bar', this.callback)
       })
 
-      return it('should return an error', function() {
-        return this.callback
-          .calledWith(new Error('resource path is outside root directory'))
-          .should.equal(true)
+      it('should return an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('resource path is outside root directory')
       })
     })
 
-    return describe('with another invalid path matching on a prefix', function() {
+    describe('with another invalid path matching on a prefix', function() {
       beforeEach(function() {
         return this.ResourceWriter.checkPath(
           'foo',
@@ -491,10 +490,11 @@ describe('ResourceWriter', function() {
         )
       })
 
-      return it('should return an error', function() {
-        return this.callback
-          .calledWith(new Error('resource path is outside root directory'))
-          .should.equal(true)
+      it('should return an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('resource path is outside root directory')
       })
     })
   })
diff --git a/test/unit/js/UrlFetcherTests.js b/test/unit/js/UrlFetcherTests.js
index e5ce52b..c435f45 100644
--- a/test/unit/js/UrlFetcherTests.js
+++ b/test/unit/js/UrlFetcherTests.js
@@ -10,6 +10,7 @@
  */
 const SandboxedModule = require('sandboxed-module')
 const sinon = require('sinon')
+const { expect } = require('chai')
 require('chai').should()
 const modulePath = require('path').join(__dirname, '../../../app/js/UrlFetcher')
 const { EventEmitter } = require('events')
@@ -140,10 +141,11 @@ describe('UrlFetcher', function() {
         return this.urlStream.emit('end')
       })
 
-      return it('should call the callback with an error', function() {
-        return this.callback
-          .calledWith(new Error('URL returned non-success status code: 404'))
-          .should.equal(true)
+      it('should call the callback with an error', function() {
+        this.callback.calledWith(sinon.match(Error)).should.equal(true)
+
+        const message = this.callback.args[0][0].message
+        expect(message).to.include('URL returned non-success status code: 404')
       })
     })