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
@@ -181,53 +181,113 @@
     );
   });
 }
 
 /**
- * Create a login form and insert into contents dom, replacing its childs if any.
+ * Create a login form and insert into contents dom (identified by id
+ * `content`). If the form (identified by its number) is already present in the
+ * dom, it gets replaced.
+ *
+ * @param {number} [num = 1] - number of the form, used as id, eg `form1`
+ * @param {string} [action = ""] - action attribute of the form
+ * @param {string} [autocomplete  = null] - forms autocomplete attribute. Default is none
+ * @param {object} [username = {}] - object describing attributes to the username field:
+ * @param {string} [username.id = null] - id of the field
+ * @param {string} [username.name = "uname"] - name attribute
+ * @param {string} [username.type = "text"] - type of the field
+ * @param {string} [username.value = null] - initial value of the field
+ * @param {string} [username.autocomplete = null] - autocomplete attribute
+ * @param {object} [password = {}] - an object describing attributes to the password field. If falsy, do not create a password field
+ * @param {string} [password.id = null] - id of the field
+ * @param {string} [password.name = "pword"] - name attribute
+ * @param {string} [password.type = "password"] - type of the field
+ * @param {string} [password.value = null] - initial value of the field
+ * @param {string} [password.label = null] - if present, wrap field in a label containing its value
+ * @param {string} [password.autocomplete = null] - autocomplete attribute
+ *
  * @return {HTMLDomElement} the form
  */
 function createLoginForm({
+  num = 1,
   action = "",
-  username = {
-    value: "",
-  },
-  password = {
-    type: "password",
-  },
+  autocomplete = null,
+  username = {},
+  password = {},
 } = {}) {
-  info(`Creating login form ${JSON.stringify({ action, username, password })}`);
+  username.id ||= null;
+  username.name ||= "uname";
+  username.type ||= "text";
+  username.value ||= null;
+  username.autocomplete ||= null;
+  password.id ||= null;
+  password.name ||= "pword";
+  password.type ||= "password";
+  password.value ||= null;
+  password.label ||= null;
+  password.autocomplete ||= null;
+
+  info(
+    `Creating login form ${JSON.stringify({ num, action, username, password })}`
+  );
 
   const form = document.createElement("form");
+  form.id = `form${num}`;
   form.action = action;
+  form.onsubmit = () => false;
+
+  if (autocomplete != null) {
+    form.setAttribute("autocomplete", autocomplete);
+  }
 
   const usernameInput = document.createElement("input");
-  usernameInput.type = "text";
-  usernameInput.name = "uname";
-  usernameInput.value = username.value;
-  if (username.autocomplete) {
+  if (username.id != null) {
+    usernameInput.id = username.id;
+  }
+  usernameInput.type = username.type;
+  usernameInput.name = username.name;
+  if (username.value != null) {
+    usernameInput.value = username.value;
+  }
+  if (username.autocomplete != null) {
     usernameInput.setAttribute("autocomplete", username.autocomplete);
   }
   form.appendChild(usernameInput);
 
   if (password) {
     const passwordInput = document.createElement("input");
+    if (password.id != null) {
+      passwordInput.id = password.id;
+    }
     passwordInput.type = password.type;
-    passwordInput.name = "pword";
-    form.appendChild(passwordInput);
+    passwordInput.name = password.name;
+    if (password.value != null) {
+      passwordInput.value = password.value;
+    }
+    if (password.autocomplete != null) {
+      passwordInput.setAttribute("autocomplete", password.autocomplete);
+    }
+    if (password.label != null) {
+      const passwordLabel = document.createElement("label");
+      passwordLabel.innerText = password.label;
+      passwordLabel.appendChild(passwordInput);
+      form.appendChild(passwordLabel);
+    } else {
+      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);
+  const oldForm = document.getElementById(form.id);
+  if (oldForm) {
+    content.replaceChild(form, oldForm);
   } else {
     content.appendChild(form);
   }
 
   return form;