Partial Comparisons

The ability to compare two instances of the same type without encumbering production code with test-specific equality methods is often helpful when writing tests, but in some cases only a subset of the properties for a given object need to be verified. ExpectedObjects facilitates this scenario by allowing comparisons against an anonymous object which defines only a subset of the expected object graph through the ShouldMatch extension method.

The following example shows how a subset of the expected values for a Customer object may be verified:

using ExpectedObjects;
using Xunit;

namespace MyProject.Specs
{
  public class CustomerSpecs
  {        
    [Fact]
    public void ComparingEqualCustomers_ShouldBeEqual()
    {
      // establish context
      var expectedCustomer = new
      {
        FirstName = "Silence",                                
        Address = new
        {                                                       
          City = "Boston",
          State = "MA",
          PostalCode = "02114"
        }                                            
      }.ToExpectedObject();

      var actualCustomer = new Customer
      {
        FirstName = "Silence",
        LastName = "Dogood",
        Address = new Address
        {
          AddressLineOne = "The New-England Courant",
          AddressLineTwo = "3 Queen Street",
          City = "Boston",
          State = "MA",
          PostalCode = "02114"
        }                                            
      };  


      // observation
      expectedCustomer.ShouldMatch(actualCustomer);
    }
  }
}