diff --git a/app/Login.py b/app/Login.py
index d82a6d1..efd0ab4 100644
--- a/app/Login.py
+++ b/app/Login.py
@@ -79,6 +79,8 @@ class UserName:
     def validate(self):
         if len(self.username) > 20:
             return f'{self.username} is too long.  The user name cannot exceed 20 characters.'
+        if len(self.username) == 0: # 用户名必须不为空
+            return 'You can`t use an empty user name.'
         if self.username.startswith('.'):  # a user name must not start with a dot
             return 'Period (.) is not allowed as the first letter in the user name.'
         if ' ' in self.username:  # a user name must not include a whitespace
diff --git a/app/templates/signup.html b/app/templates/signup.html
index 48cf932..46d9a2e 100644
--- a/app/templates/signup.html
+++ b/app/templates/signup.html
@@ -29,8 +29,8 @@
         password2 = $("#password2").val().trim();
 
         // 基本表单验证
-        if (username === "" || password === "" || password2 === "") {
-            alert('输入不能为空!');
+        if (password === "" || password2 === "") {
+            alert('输入密码不能为空!');
             return false;
         }
         if (password.includes(' ') || password2.includes(' ')) {
diff --git a/app/test/test_integration_login.py b/app/test/test_integration_login.py
new file mode 100644
index 0000000..793c4d7
--- /dev/null
+++ b/app/test/test_integration_login.py
@@ -0,0 +1,74 @@
+# test_integration_username.py
+
+import pytest
+import sys
+import os
+
+# 获取文件所在目录的上两级目录（EnglishPal）
+project_root = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..'))
+sys.path.append(project_root)
+
+from app.Login import add_user, check_username_availability
+
+
+# 模拟数据库行为
+class MockUserDB:
+    def __init__(self):
+        self.users = {}
+
+    def insert_user(self, username, password, start_date, expiry_date):
+        if username in self.users:
+            return False
+        self.users[username] = {
+            'password': password,
+            'start_date': start_date,
+            'expiry_date': expiry_date
+        }
+        return True
+
+    def get_user_by_username(self, username):
+        return self.users.get(username)
+
+
+original_insert_user = None
+original_get_user_by_username = None
+
+
+@pytest.fixture(autouse=True)
+def setup_and_teardown():
+    global original_insert_user, original_get_user_by_username
+
+    from app.Login import insert_user as original_iu, get_user_by_username as original_gubu
+    original_insert_user = original_iu
+    original_get_user_by_username = original_gubu
+
+    mock_db = MockUserDB()
+
+    def mock_insert_user(**kwargs):
+        return mock_db.insert_user(**kwargs)
+
+    def mock_get_user_by_username(username):
+        return mock_db.get_user_by_username(username)
+
+    from app.Login import insert_user, get_user_by_username
+    insert_user = mock_insert_user
+    get_user_by_username = mock_get_user_by_username
+
+    yield
+
+    from app.Login import insert_user, get_user_by_username
+    insert_user = original_insert_user
+    get_user_by_username = original_get_user_by_username
+
+
+def test_add_user_with_empty_username_fails():
+    with pytest.raises(ValueError) as exc_info:
+        add_user('', 'Password123')
+    assert "Attribute User.name is required" in str(exc_info.value)
+
+
+def test_add_user_with_valid_username_succeeds():
+    result = add_user('validuser', 'Password123')
+    assert result is None  # 如果 add_user 不返回值，则断言无异常即可
+    assert check_username_availability('validuser') is False  # 用户已存在
+
diff --git a/app/test_login.py b/app/test_login.py
new file mode 100644
index 0000000..cd8f418
--- /dev/null
+++ b/app/test_login.py
@@ -0,0 +1,63 @@
+# test_username.py
+
+import pytest
+from app.Login import UserName
+
+
+def test_username_too_long():
+    username = 'a' * 21
+    result = UserName(username).validate()
+    assert username in result
+    assert 'too long' in result
+
+
+def test_username_empty():
+    username = ''
+    result = UserName(username).validate()
+    assert 'empty user name' in result
+
+
+def test_username_starts_with_dot():
+    username = '.startwithdot'
+    result = UserName(username).validate()
+    assert 'Period (.) is not allowed' in result
+
+
+def test_username_contains_space():
+    username = 'has space'
+    result = UserName(username).validate()
+    assert 'Whitespace is not allowed' in result
+
+
+def test_username_contains_invalid_punctuation():
+    invalid_chars = ['@', '#', '$', '!', '{', '}', '[', ']']
+    for c in invalid_chars:
+        username = f'bad{c}name'
+        result = UserName(username).validate()
+        assert f'{c} is not allowed' in result, f"Failed on char: {c}"
+
+
+def test_username_uses_restricted_word():
+    restricted_words = ['signup', 'login', 'logout', 'reset', 'mark', 'back',
+                        'unfamiliar', 'familiar', 'del', 'admin']
+    for word in restricted_words:
+        result = UserName(word).validate()
+        assert 'restricted word' in result, f"Failed on word: {word}"
+
+
+def test_username_contains_chinese():
+    username = '用户名'
+    result = UserName(username).validate()
+    assert 'Chinese characters are not allowed' in result
+
+
+def test_valid_username():
+    valid_usernames = [
+        'valid_user',
+        'valid.user',
+        'user123',
+        'A_veryValidName',
+    ]
+    for username in valid_usernames:
+        result = UserName(username).validate()
+        assert result == 'OK', f"Failed on valid username: {username}"
diff --git a/current_branch_commit_messages.txt b/current_branch_commit_messages.txt
new file mode 100644
index 0000000..06f4fac
Binary files /dev/null and b/current_branch_commit_messages.txt differ