anchor.diff:  open System
   open System.Reflection
   
  +/// <summary>
  +/// Encapsulates a unit test verifying that the return value for a public Query
  +/// (a method that returns a value) is not null.
  +/// </summary>
   type ReturnValueMustNotBeNullAssertion (builder) =
       inherit IdiomaticAssertion()
       
  
positive.code:         if (getMethod <> null) then 
              this.Verify(propertyInfo.GetGetMethod());
  
      override this.Verify (methodInfo : MethodInfo) =
          if methodInfo = null then 
              raise <| ArgumentNullException("methodInfo")
  
negative.code: 
      let Create specimen = SpecimenContext(builder).Resolve(specimen)
      
      /// Gets the <see cref="ISpecimenBuilder"/> which create instances if the
      /// public Query is an instance method.
      member this.Builder = builder
  
      /// <summary>
      /// Verifies that the return value for a Property is not null.
      /// </summary>
      /// <param name="propertyInfo">The property to verify.</param>
      override this.Verify (propertyInfo : PropertyInfo) =
          if propertyInfo = null then 
              raise <| ArgumentNullException("propertyInfo")
  