how is unit testing done code example

Example 1: what is unit testing

UNIT TESTING is a  software testing where individual
units or components of a software are tested.
The purpose is to validate that each unit of the 
software performs as designed.

Example 2: what is a unit testable code

public class SomeClass
{
    public SomeClass(calculatedParams)
    {
        ...
    }
}

    public interface ISomeClassCreator
    {
        SomeClass Create(params);
    }

public class SomeClassCreator: ISomeClassCreator
{
    public SomeClass Create(params)
    {
        ...
    }
}