diff --git a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
--- a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
+++ b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
@@ -181,10 +181,61 @@
     );
   });
 }
 
 /**
+ * Create a login form and insert into contents dom, replacing its childs if any.
+ * @return {HTMLDomElement} the form
+ */
+function createLoginForm({
+  action = "",
+  username = {
+    value: "",
+  },
+  password = {
+    type: "password",
+  },
+} = {}) {
+  info(`Creating login form ${JSON.stringify({ action, username, password })}`);
+
+  const form = document.createElement("form");
+  form.action = action;
+
+  const usernameInput = document.createElement("input");
+  usernameInput.type = "text";
+  usernameInput.name = "uname";
+  usernameInput.value = username.value;
+  if (username.autocomplete) {
+    usernameInput.setAttribute("autocomplete", username.autocomplete);
+  }
+  form.appendChild(usernameInput);
+
+  if (password) {
+    const passwordInput = document.createElement("input");
+    passwordInput.type = password.type;
+    passwordInput.name = "pword";
+    form.appendChild(passwordInput);
+  }
+
+  const submitButton = document.createElement("button");
+  submitButton.type = "submit";
+  submitButton.name = "submit";
+  submitButton.innerText = "Submit";
+  form.appendChild(submitButton);
+
+  const content = document.getElementById("content");
+
+  if (content.firstChild) {
+    content.replaceChild(form, content.firstChild);
+  } else {
+    content.appendChild(form);
+  }
+
+  return form;
+}
+
+/**
  * Check for expected username/password in form.
  * @see `checkForm` below for a similar function.
  */
 function checkLoginForm(
   usernameField,
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
@@ -18,52 +18,21 @@
 <p id="display"></p>
 <!-- we presumably can't hide the content for this test. -->
 <div id="content"></div>
 <pre id="test">
 <script class="testbody" type="text/javascript">
-function createForm () {
-  const form = document.createElement("form");
-  form.action = "https://autocomplete:8888/formtest.js";
-
-  const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  form.appendChild(usernameInput);
-
-  const passwordInput = document.createElement("input");
-  passwordInput.type = "password";
-  passwordInput.name = "pword";
-  form.appendChild(passwordInput);
-
-  const submitButton = document.createElement("button");
-  submitButton.type = "submit";
-  submitButton.name = "submit";
-  submitButton.innerText = "Submit";
-  form.appendChild(submitButton);
-
-  const content = document.getElementById("content");
-
-  if (content.firstChild) {
-    content.replaceChild(form, content.firstChild);
-  } else {
-    content.appendChild(form);
-  }
-
-  return form;
-}
-
 /** Test for Login Manager: multiple login autocomplete. **/
 
 add_setup(async () => {
   await addLoginsInParent(
     [window.location.origin, "https://differentFormSubmitURL", null, "dfsu1", "dfsp1", "uname", "pword"]
   );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
-  const form = createForm();
+  const form = createLoginForm();
 
   await SimpleTest.promiseFocus(window);
 
   // Make sure initial form is empty.
   checkLoginForm(form.uname, "", form.pword, "");
@@ -74,11 +43,11 @@
 /* For this testcase, the only login that exists for this origin
  * is one with a different formActionOrigin, so the login will appear
  * in the autocomplete popup.
  */
 add_task(async function test_form1_menu_shows_logins_for_different_formActionOrigin() {
-  const form = createForm();
+  const form = createLoginForm();
 
   await SimpleTest.promiseFocus(window);
 
   // Trigger autocomplete popup
   form.uname.value = "";
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
@@ -13,43 +13,12 @@
 Login Manager test: related realms autocomplete
 <p id="display"></p>
 <div id="content"></div>
 <pre id="test">
 <script class="testbody" type="text/javascript">
-
 /** Test for Login Manager: related realms autocomplete. **/
 
-function createForm () {
-  const form = document.createElement("form");
-
-  const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  form.appendChild(usernameInput);
-
-  const passwordInput = document.createElement("input");
-  passwordInput.type = "password";
-  passwordInput.name = "pword";
-  form.appendChild(passwordInput);
-
-  const submitButton = document.createElement("button");
-  submitButton.type = "submit";
-  submitButton.name = "submit";
-  submitButton.innerText = "Submit";
-  form.appendChild(submitButton);
-
-  const content = document.getElementById("content");
-
-  if (content.firstChild) {
-    content.replaceChild(form, content.firstChild);
-  } else {
-    content.appendChild(form);
-  }
-
-  return form;
-}
-
 function sendFakeAutocompleteEvent(element) {
   var acEvent = document.createEvent("HTMLEvents");
   acEvent.initEvent("DOMAutoComplete", true, false);
   element.dispatchEvent(acEvent);
 }
@@ -74,20 +43,20 @@
   );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
-  const form = createForm();
+  const form = createLoginForm();
 
   // Make sure initial form is empty.
   checkLoginForm(form.uname, "", form.pword, "");
   const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is initially closed");
 });
 
 add_task(async function test_form_related_domain_menuitems() {
-  const form = createForm();
+  const form = createLoginForm();
 
   form.uname.focus();
 
   const autocompleteItems = await popupByArrowDown();
   const popupState = await getPopupState();
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
@@ -15,41 +15,10 @@
 
 <!-- we presumably can't hide the content for this test. -->
 <div id="content"></div>
 <pre id="test">
 <script class="testbody" type="text/javascript">
-function createForm () {
-  const form = document.createElement("form");
-  form.action = "https://otherexample.com/formtest.js"
-
-  const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  form.appendChild(usernameInput);
-
-  const passwordInput = document.createElement("input");
-  passwordInput.type = "password";
-  passwordInput.name = "pword";
-  form.appendChild(passwordInput);
-
-  const submitButton = document.createElement("button");
-  submitButton.type = "submit";
-  submitButton.name = "submit";
-  submitButton.innerText = "Submit";
-  form.appendChild(submitButton);
-
-  const content = document.getElementById("content");
-
-  if (content.firstChild) {
-    content.replaceChild(form, content.firstChild);
-  } else {
-    content.appendChild(form);
-  }
-
-  return form;
-}
-
 const setupScript = runInParent(function setup() {
   addMessageListener("getDateString", () => {
     const dateAndTimeFormatter = new Services.intl.DateTimeFormat(undefined, { dateStyle: "medium" });
     return dateAndTimeFormatter.format(new Date());
   });
@@ -83,11 +52,13 @@
   });
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
-  const form = createForm();
+  const form = createLoginForm({
+    action: "https://otherexample.com/formtest.js"
+  });
 
   // Make sure initial form is empty.
   checkLoginForm(form.uname, "", form.pword, "");
   const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is initially closed");
@@ -96,11 +67,13 @@
 /* For this testcase, there exists two logins for this origin
  * on different subdomains but with different passwords. Both logins
  * should appear in the autocomplete popup.
  */
 add_task(async function test_form1_menu_shows_two_logins_same_usernames_for_different_subdomain() {
-  const form = createForm();
+  const form = createLoginForm({
+    action: "https://otherexample.com/formtest.js"
+  });
 
   // Trigger autocomplete popup
   form.uname.focus();
 
   const autocompleteItems = await popupByArrowDown();
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
@@ -16,46 +16,24 @@
 <script>
 const { ContentTaskUtils } = SpecialPowers.ChromeUtils.import(
   "resource://testing-common/ContentTaskUtils.jsm"
 );
 
-function createForm () {
-  const form = document.createElement("form");
-  form.action = "https://autocomplete"
-
-  const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  usernameInput.setAttribute("autocomplete", "username");
-  form.appendChild(usernameInput);
-
-  const submitButton = document.createElement("button");
-  submitButton.type = "submit";
-  submitButton.name = "submit";
-  submitButton.innerText = "Submit";
-  form.appendChild(submitButton);
-
-  const content = document.getElementById("content");
-
-  if (content.firstChild) {
-    content.replaceChild(form, content.firstChild);
-  } else {
-    content.appendChild(form);
-  }
-
-  return form;
-}
-
 add_setup(async () => {
   await addLoginsInParent(
     [location.origin, "https://autocomplete", null, "user1", "pass1", "", ""],
     [location.origin, "https://autocomplete", null, "user2", "pass2", "", ""]
   );
 });
 
 add_task(async function test_username_field_in_username_only_form_highlight_on_autocomplete() {
-  const form = createForm();
+  const form = createLoginForm({
+    action: "https://autocomplete",
+    username: {
+      autocomplete: "username"
+    }
+  });
 
   await openPopupOn(form.uname);
   synthesizeKey("KEY_ArrowDown");
   await synthesizeKey("KEY_Enter");
 
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_input_events.html b/toolkit/components/passwordmgr/test/mochitest/test_input_events.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_input_events.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_input_events.html
@@ -12,63 +12,41 @@
 Login Manager test: input events should fire.
 <p id="display"></p>
 <div id="content" style="display: none"></div>
 <pre id="test"></pre>
 <script>
-  function setupForm () {
-    const form = document.createElement("form");
-
-    const usernameInput = document.createElement("input");
-    usernameInput.type = "text";
-    usernameInput.name = "username";
-    form.appendChild(usernameInput);
-    const passwordInput = document.createElement("input");
-    passwordInput.type = "password";
-    passwordInput.name = "password";
-    form.appendChild(passwordInput);
-
-    const content = document.getElementById("content")
-    if (content.firstChild) {
-      content.replaceChild(form, content.firstChild);
-    } else {
-      content.appendChild(form);
-    }
-
-    return form;
-  }
-
   add_setup(async () => {
     await setStoredLoginsAsync(
       [location.origin, location.origin, null, "testuser", "testpass", "uname", "pword"]
     );
   })
 
   add_task(async function username_events() {
     return new Promise(resolve => {
       let inputFired = false;
-      const form = setupForm();
-      form.username.oninput = e => {
+      const form = createLoginForm();
+      form.uname.oninput = e => {
         is(e.target.value, "testuser", "Should get 'testuser' as value in input event");
         inputFired = true;
       };
-      form.username.onchange = e => {
+      form.uname.onchange = e => {
         ok(inputFired, "Should get input event before change event for username field.");
         is(e.target.value, "testuser", "Should get 'testuser' as value in change event");
         resolve();
       };
     })
   })
 
   add_task(async function password_events() {
     return new Promise(resolve => {
       let inputFired = false;
-      const form = setupForm();
-      form.password.oninput = e => {
+      const form = createLoginForm();
+      form.pword.oninput = e => {
         is(e.target.value, "testpass", "Should get 'testpass' as value in input event");
         inputFired = true;
       };
-      form.password.onchange = e => {
+      form.pword.onchange = e => {
         ok(inputFired, "Should get input event before change event for password field.");
         is(e.target.value, "testpass", "Should get 'testpass' as value in change event");
         resolve();
       };
     })
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html b/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
@@ -13,50 +13,10 @@
 <body>
 <p id="display"></p>
 <div id="content"></div>
 <pre id="test">
 <script class="testbody" type="text/javascript">
-function createForm (heading, {
-  action,
-  usernameInputValue = "",
-  passwordInputType = "password"
-}) {
-  const form = document.createElement("form");
-  form.action = action;
-
-  const h = document.createElement("h4");
-  h.innerText = heading;
-  form.appendChild(h);
-
-  const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  usernameInput.value = usernameInputValue;
-  form.appendChild(usernameInput);
-
-  const passwordInput = document.createElement("input");
-  passwordInput.type = passwordInputType;
-  passwordInput.name = "pword";
-  form.appendChild(passwordInput);
-
-  const submitButton = document.createElement("button");
-  submitButton.type = "submit";
-  submitButton.name = "submit";
-  submitButton.innerText = "Submit";
-  form.appendChild(submitButton);
-
-  const content = document.getElementById("content");
-
-  if (content.firstChild) {
-    content.replaceChild(form, content.firstChild);
-  } else {
-    content.appendChild(form);
-  }
-
-  return form;
-}
-
 const action1 = "http://username-focus-1";
 const action2 = "http://username-focus-2";
 
 add_setup(async () => {
   await addLoginsInParent(
@@ -65,11 +25,11 @@
     [location.origin, action2, null, "testuser2B", "testpass2B", "", ""]
   );
 });
 
 add_task(async function autofilled() {
-  const form = createForm("autofilled", { action: action1 });
+  const form = createLoginForm({ action: action1 });
 
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => form.uname.focus());
 
   form.submit.focus();
@@ -77,13 +37,15 @@
   info("Focus when we don't have an exact match");
   await popupBy(() => form.uname.focus());
 });
 
 add_task(async function autofilled_prefilled_un() {
-  const form = createForm("autofilled prefilled un", {
+  const form = createLoginForm({
     action: action1,
-    usernameInputValue: "testuser1A"
+    username: {
+      value: "testuser1A"
+    }
   });
 
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => form.uname.focus());
 
@@ -92,13 +54,15 @@
   info("Focus when we don't have an exact match");
   await popupBy(() => form.uname.focus());
 });
 
 add_task(async function autofilled_focused_dynamic() {
-  const form = createForm("autofilled focused dynamic", {
+  const form = createLoginForm({
     action: action1,
-    passwordInputType: "not-yet-password"
+    password: {
+      type: "not-yet-password"
+    }
   });
 
   info("Username and password will be filled while username focused");
   await noPopupBy(() => form.uname.focus());
 
@@ -115,33 +79,37 @@
 });
 
 // Begin testing forms that have multiple saved logins
 
 add_task(async function multiple() {
-  const form = createForm("multiple", { action: action2 });
+  const form = createLoginForm({ action: action2 });
 
   info("Fields not filled due to multiple so autocomplete upon focus");
   await popupBy(() => form.uname.focus());
 });
 
 add_task(async function multiple_dynamic() {
-  const form = createForm("multiple dynamic", {
+  const form = createLoginForm({
     action: action2,
-    passwordInputType: "not-yet-password"
+    password: {
+      type: "not-yet-password"
+    }
   });
 
   info("Fields not filled but username is focused upon marking so open");
   await noPopupBy(() => form.uname.focus());
 
   info("triggering _fillForm code");
   await popupBy(() => form.pword.type = "password");
 });
 
 add_task(async function multiple_prefilled_un1() {
-  const form = createForm("multiple prefilled un1", {
+  const form = createLoginForm({
     action: action2,
-    usernameInputValue: "testuser2A"
+    username: {
+      value: "testuser2A"
+    }
   });
 
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => form.uname.focus());
 
@@ -150,13 +118,15 @@
   info("Focus when we don't have an exact match");
   await popupBy(() => form.uname.focus());
 });
 
 add_task(async function multiple_prefilled_un2() {
-  const form = createForm("multiple prefilled un2", {
+  const form = createLoginForm({
     action: action2,
-    usernameInputValue: "testuser2B"
+    username: {
+      value: "testuser2B"
+    }
   });
 
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => form.uname.focus());
 
@@ -165,14 +135,18 @@
   info("Focus when we don't have an exact match");
   await popupBy(() => form.uname.focus());
 });
 
 add_task(async function multiple_prefilled_focused_dynamic() {
-  const form = createForm("multiple prefilled focused dynamic", {
+  const form = createLoginForm({
     action: action2,
-    usernameInputValue: "testuser2B",
-    passwordInputType: "not-yet-password"
+    username: {
+      value: "testuser2B"
+    },
+    password: {
+      type: "not-yet-password"
+    }
   });
 
   info("Username and password will be filled while username focused");
   await noPopupBy(() => form.uname.focus());
   info("triggering autofill");