Compare 2 not identical DTO but have common properties in Fluent Assertion

December 9, 2021

I am writing a unit test for a manual mapper. It maps an object to two different classes but have common properties. how to compare if their properties are equal in fluent assertion?

This is what I tried

 var domain = new Domain.ConsentDefinition()
{
     SomeProperty = 1,
     ListOfFirstDTO = new List<FirstDTO>()
     {
          new FirstDTO()
          {
             Name = "Label",
             Age = 18,
          }
     },
     SomeOtherProperty = "one"
}

ef = domain.ToEF();

domain.SomeProperty.Should().Be(ef.SomeProperty);
domain.SomeOtherProperty.Should().Be(ef.SomeOtherProperty);
domain.ListFirstDTO.Should().Equal(ef.ListOfSecondDTO); // This is NOT working

classes

public class FirstDTO
{
   public string Name {get;set;}
   public int Age {get;set;}
}

public class SecondDTO
{
   public string Name {get;set;}
   public int Age {get;set;}
   public string Email {get;set;}
}

>Solution :

Override firstDTO’s equals so you compare values instead of references:


        public override bool Equals(object obj)
        {
            if (obj == null || !(obj is FirstDTO) || !(obj is SecondDTO))
            {
                return false;
            }
            
            if(obj is SecondDTO){
              return (this.Name == ((SecondDTO)obj).Name)
                && (this.Age == ((SecondDTO)obj).Age)

            }
            // if obj is instance of FirstDTO check the rest of fields...
        }

and run again

 domain.ListFirstDTO.Should().Equal(ef.ListOfSecondDTO); // This is NOT working

Another more elegant solution with no need of overriding equals would be


domain.ListFirstDTO.Select(c => c.Name).Should().Equal(ef.ListOfSecondDTO.Select(c => c.Name);

domain.ListFirstDTO.Select(c => c.Age).Should().Equal(ef.ListOfSecondDTO.Select(c => c.Age);

fluentassertion/collections