how to write tests that impersonates different users?

Question

My Winforms app set permissions based on the group membership found in the current process.

I just made a unit test in MSTEST.

I'd like to run it as other users so I can verify the expected behavior.

Here's what I'm kind of shooting for:

    [TestMethod]
    public void SecuritySummaryTest1()
    {
        Impersonate(@"SomeDomain\AdminUser", password);
        var target = new DirectAgentsSecurityManager();
        string actual = target.SecuritySummary;
        Assert.AreEqual(
            @"Default=[no]AccountManagement=[no]MediaBuying=[no]AdSales=[no]Accounting=[no]Admin=[YES]", actual);
    }
    [TestMethod]
    public void SecuritySummaryTest2()
    {
        Impersonate(@"SomeDomain\AccountantUser", password);
        var target = new DirectAgentsSecurityManager();
        string actual = target.SecuritySummary;
        Assert.AreEqual(
            @"Default=[no]AccountManagement=[YES]MediaBuying=[no]AdSales=[no]Accounting=[YES]Admin=[NO]", actual);
    }

Answer 1

public class UserCredentials
{
    private readonly string _domain;
    private readonly string _password;
    private readonly string _username;

    public UserCredentials(string domain, string username, string password)
    {
        _domain = domain;
        _username = username;
        _password = password;
    }

    public string Domain { get { return _domain; } }
    public string Username { get { return _username; } }
    public string Password { get { return _password; } }
}
public class UserImpersonation : IDisposable
{
    private readonly IntPtr _dupeTokenHandle = new IntPtr(0);
    private readonly IntPtr _tokenHandle = new IntPtr(0);
    private WindowsImpersonationContext _impersonatedUser;

    public UserImpersonation(UserCredentials credentials)
    {
        const int logon32ProviderDefault = 0;
        const int logon32LogonInteractive = 2;
        const int securityImpersonation = 2;

        _tokenHandle = IntPtr.Zero;
        _dupeTokenHandle = IntPtr.Zero;

        if (!Advapi32.LogonUser(credentials.Username, credentials.Domain, credentials.Password,
                                logon32LogonInteractive, logon32ProviderDefault, out _tokenHandle))
        {
            var win32ErrorNumber = Marshal.GetLastWin32Error();

            // REVIEW: maybe ImpersonationException should inherit from win32exception
            throw new ImpersonationException(win32ErrorNumber, new Win32Exception(win32ErrorNumber).Message,
                                             credentials.Username, credentials.Domain);
        }

        if (!Advapi32.DuplicateToken(_tokenHandle, securityImpersonation, out _dupeTokenHandle))
        {
            var win32ErrorNumber = Marshal.GetLastWin32Error();

            Kernel32.CloseHandle(_tokenHandle);
            throw new ImpersonationException(win32ErrorNumber, "Unable to duplicate token!", credentials.Username,
                                             credentials.Domain);
        }

        var newId = new WindowsIdentity(_dupeTokenHandle);
        _impersonatedUser = newId.Impersonate();
    }

    public void Dispose()
    {
        if (_impersonatedUser != null)
        {
            _impersonatedUser.Undo();
            _impersonatedUser = null;

            if (_tokenHandle != IntPtr.Zero)
                Kernel32.CloseHandle(_tokenHandle);

            if (_dupeTokenHandle != IntPtr.Zero)
                Kernel32.CloseHandle(_dupeTokenHandle);
        }
    }
}

internal static class Advapi32
{
    [DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool DuplicateToken(IntPtr ExistingTokenHandle, int SECURITY_IMPERSONATION_LEVEL,
                                             out IntPtr DuplicateTokenHandle);

    [DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword,
                                        int dwLogonType, int dwLogonProvider, out IntPtr phToken);
}

internal static class Kernel32
{
    [DllImport("kernel32.dll", SetLastError = true)]
    [return : MarshalAs(UnmanagedType.Bool)]
    public static extern bool CloseHandle(IntPtr hObject);
}

I didn't include the implementation of ImpersonationException but it's not important. It doesn't do anything special.