feat: add jsdom for browser-ish tests

test/package.json

 {
-  "#": "We must put jest in a sub-directory otherwise VS Code somehow picks up",
   "#": "the types and generates conflicts with mocha.",
   "devDependencies": {
     "@types/jest": "^26.0.20",
+    "@types/jsdom": "^16.2.6",
     "@types/node-fetch": "^2.5.8",
     "@types/supertest": "^2.0.10",
     "jest": "^26.6.3",
+    "jsdom": "^16.4.0",
     "node-fetch": "^2.6.1",
     "playwright": "^1.8.0",
     "supertest": "^6.1.1",

test/yarn.lock

@@ -551,6 +551,15 @@
     jest-diff "^26.0.0"
     pretty-format "^26.0.0"
 
+"@types/jsdom@^16.2.6":
+  version "16.2.6"
+  resolved "https://registry.yarnpkg.com/@types/jsdom/-/jsdom-16.2.6.tgz#9ddf0521e49be5365797e690c3ba63148e562c29"
+  integrity sha512-yQA+HxknGtW9AkRTNyiSH3OKW5V+WzO8OPTdne99XwJkYC+KYxfNIcoJjeiSqP3V00PUUpFP6Myoo9wdIu78DQ==
+  dependencies:
+    "@types/node" "*"
+    "@types/parse5" "*"
+    "@types/tough-cookie" "*"
+
 "@types/node-fetch@^2.5.8":
   version "2.5.8"
   resolved "https://registry.yarnpkg.com/@types/node-fetch/-/node-fetch-2.5.8.tgz#e199c835d234c7eb0846f6618012e558544ee2fb"
@@ -569,6 +578,11 @@
   resolved "https://registry.yarnpkg.com/@types/normalize-package-data/-/normalize-package-data-2.4.0.tgz#e486d0d97396d79beedd0a6e33f4534ff6b4973e"
   integrity sha512-f5j5b/Gf71L+dbqxIpQ4Z2WlmI/mPJ0fOkGGmFgtb6sAu97EPczzbS3/tJKxmcYDj55OX6ssqwDAWOHIYDRDGA==
 
+"@types/parse5@*":
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/@types/parse5/-/parse5-6.0.0.tgz#38590dc2c3cf5717154064e3ee9b6947ee21b299"
+  integrity sha512-oPwPSj4a1wu9rsXTEGIJz91ISU725t0BmSnUhb57sI+M8XEmvUop84lzuiYdq0Y5M6xLY8DBPg0C2xEQKLyvBA==
+
 "@types/prettier@^2.0.0":
   version "2.1.6"
   resolved "https://registry.yarnpkg.com/@types/prettier/-/prettier-2.1.6.tgz#f4b1efa784e8db479cdb8b14403e2144b1e9ff03"
@@ -594,6 +608,11 @@
   dependencies:
     "@types/superagent" "*"
 
+"@types/tough-cookie@*":
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/@types/tough-cookie/-/tough-cookie-4.0.0.tgz#fef1904e4668b6e5ecee60c52cc6a078ffa6697d"
+  integrity sha512-I99sngh224D0M7XgW1s120zxCt3VYQ3IQsuw3P3jbq5GG4yc79+ZjyKznyOGIQrflfylLgcfekeZW/vk0yng6A==
+
 "@types/yargs-parser@*":
   version "20.2.0"
   resolved "https://registry.yarnpkg.com/@types/yargs-parser/-/yargs-parser-20.2.0.tgz#dd3e6699ba3237f0348cd085e4698780204842f9"