Question

This is my simple code.

public class Permission
  {
    public string Name { get; set; }
    public bool IsEnable { get; set; }
  }

  public class User
  {
    public virtual List<Permission> Permissions { get; set; }

    public bool ContainPermission(string permissionName)
    {      
      var result = Permissions.Where(p => p.Name == permissionName && p.IsEnable).FirstOrDefault();
      return result != null;
    }
  }

And I want to test method ContainPermission.
I am using Moq and write this code:

[TestClass]
  public class UserPermissionTest
  {
    [TestMethod]
    public void UserContainPermission_WhenPermissionEnable_ReturnTrue()
    {
      var mockUser = new Mock<User>();

      mockUser.SetupGet(p => p.Permissions).Returns(
        () => new List<Permission>
                {
                  new Permission {Name = "Name", IsEnable = true}
                });

      var user = mockUser.Object;
      var isContainPermission = user.ContainPermission("Name");

      Assert.IsTrue(isContainPermission);
    }
  }

It works! Test method pass. But I decided to check it one’s more. I changed method ContainPermission:

public bool ContainPermission(string permissionName)
{
  Permissions.Clear();

  var result = Permissions.Where(p => p.Name == permissionName && p.IsEnable).FirstOrDefault();
  return result != null;
}

And my test method pass too! I don’t understand why? What’s wrong is my code?

Answer 1

Because of the following line, any time you ask for permissions you will always get a result:

mockUser.SetupGet(p => p.Permissions)

You can test that you get the required result when the collection is empty by writing another test as follows:

[TestMethod]
public void UserContainPermission_WhenNoPermissions_ReturnFalse()
{
  var mockUser = new Mock<User>();

  mockUser.SetupGet(p => p.Permissions).Returns(
    () => new List<Permission>());

  var user = mockUser.Object;
  var isContainPermission = user.ContainPermission("Name");

  Assert.IsFalse(isContainPermission);
}