ExpectedException in nUnit gave me an error

If you’re using NUnit 3.0, then your error is because the ExpectedExceptionAttribute has been removed. You should instead use a construct like the Throws Constraint.

For example, the tutorial you linked has this test:

[Test]
[ExpectedException(typeof(InsufficientFundsException))]
public void TransferWithInsufficientFunds()
{
    Account source = new Account();
    source.Deposit(200m);

    Account destination = new Account();
    destination.Deposit(150m);

    source.TransferFunds(destination, 300m);
}

To change this to work under NUnit 3.0, change it to the following:

[Test]
public void TransferWithInsufficientFunds()
{
    Account source = new Account();
    source.Deposit(200m);

    Account destination = new Account();
    destination.Deposit(150m);

    Assert.That(() => source.TransferFunds(destination, 300m), 
                Throws.TypeOf<InsufficientFundsException>());
}