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
@@ -181,113 +181,53 @@
     );
   });
 }
 
 /**
- * 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
- *
+ * Create a login form and insert into contents dom, replacing its childs if any.
  * @return {HTMLDomElement} the form
  */
 function createLoginForm({
-  num = 1,
   action = "",
-  autocomplete = null,
-  username = {},
-  password = {},
+  username = {
+    value: "",
+  },
+  password = {
+    type: "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 })}`
-  );
+  info(`Creating login form ${JSON.stringify({ 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");
-  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.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");
-    if (password.id != null) {
-      passwordInput.id = password.id;
-    }
     passwordInput.type = password.type;
-    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);
-    }
+    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");
 
-  const oldForm = document.getElementById(form.id);
-  if (oldForm) {
-    content.replaceChild(form, oldForm);
+  if (content.firstChild) {
+    content.replaceChild(form, content.firstChild);
   } else {
     content.appendChild(form);
   }
 
   return form;