[TestMethod()]
public void Should_Password_Equal_To_ConfirmPassword()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai"，
Password = "a121ww123"，
ConfirmPassword = "a121ww1231"
};
string expected = "password is not equal to confirmPassword";
string actual = target.CreateUser(user);
Assert.AreEqual(expected， actual);
}
[TestMethod()]
public void Should_Creator_Not_Null_Or_Empty()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai"，
Password = "a121ww123"，
ConfirmPassword = "a121ww1231"
};
string expected = "password is not equal to confirmPassword";
string actual = target.CreateUser(user);
Assert.AreEqual(expected， actual);
}
[TestMethod()]
public void Should_CreateDate_Assigned_Value()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai"，
Password = "a121ww123"，
ConfirmPassword = "a121ww123"，
Creator = "ethan.cai"
};
string expected = "createdate must be assigned value";
string actual = target.CreateUser(user);
Assert.AreEqual(expected， actual);
}
[TestMethod()]
public void Should_CreatorIP_Not_Null_Or_Empty()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai"，
Password = "a121ww123"，
ConfirmPassword = "a121ww123"，
Creator = "ethan.cai"，
CreateDate = DateTime.Now
};
string expected = "creatorIP is null or empty";
string actual = target.CreateUser(user);
Assert.AreEqual(expected， actual);
}
[TestMethod()]
public void Should_Trim_Username()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai  "，
Password = "a121ww123"，
ConfirmPassword = "a121ww123"，
Creator = "ethan.cai"，
CreateDate = DateTime.Now，
CreatorIP = "127.0.0.1"
};
string expected = "ethan.cai";
target.CreateUser(user);
Assert.AreEqual(expected， user.Username);
}
[TestMethod()]
public void Should_Save_MD5_Hash_Password()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai  "，
Password = "a121ww123"，
ConfirmPassword = "a121ww123"，
Creator = "ethan.cai"，
CreateDate = DateTime.Now，
CreatorIP = "127.0.0.1"
};
string actual = target.CreateUser(user);
Assert.IsTrue("success" == actual
&& user.Password == BitConverter.ToString(MD5.Create().ComputeHash(Encoding.UTF8.GetBytes("a121ww123"))));
}
[TestMethod()]
public void Should_Create_User_Successfully_When_User_Is_OK()
{
UserBusiness target = new UserBusiness();
User user = new User()
{
Username = "ethan.cai  "，
Password = "a121ww123"，
ConfirmPassword = "a121ww123"，
Creator = "ethan.cai"，
CreateDate = DateTime.Now，
CreatorIP = "127.0.0.1"
};
string expected = "success";
string actual = target.CreateUser(user);
Assert.IsTrue(expected == actual);
}
}

　　如果仅从代码覆盖率的角度来看，单元测试Should_Trim_Username、Should_Save_MD5_Hash_Password不会增加覆盖率，似乎没有必要，但是从逻辑上看，创建的账户的Username头尾不能包含空白字符，密码也不能明文存储，显然这两个用例是非常有必要的。
　　单元测试写多少才够？这个问题没有确定的答案，但原则是让你自己觉得安全。代码覆盖率高不能保证安全，真正的安全需要用测试用例覆盖逻辑。