In a normal situation your public methods consume the private ones and when you’re testing, if you’re testing, you only test the public methods.

In Unit Testing, this assumption is totally right. You’re testing a Unit, and if you think Unit as a class then you will only test the public methods.

The question is: how can we break a public method and test only the tiny bits?

In this case we have a User class with a private method that gives a Location based on an IpAddress.

public class User
    private static string GetUserCountry(string ipAddress)
        return LookupService.GetLocation(ipAddress);

We can test this GetUserCountry using Reflection.

As GetUserCountry is a static method we’ll be using PrivateType instead of PrivateObject to instantiate the User class.

To invoke the GetUserCountry we can use PrivateType.InvokeStatic instead of PrivateObject.Invoke.

public void IpAddressLocationMustMatchWithGetUserCountry()
    var obj = new PrivateType(typeof(User));
    var method = "GetUserCountry";
    var connection = new MockConnection() { 
        IpAddress = "", 
        Country = "Portugal"

    var expected = (string)obj.InvokeStatic(method, 
        new object[] 
    Assert.AreEqual(expected, connection.Country);

Now that we can test private methods but this solution makes sense?

Is there anything wrong about testing private methods? I don’t think so.

Should you break the things up and create another class with testable public methods? Yes, you should.