/Extensions/src/Ncqrs.EventBus.Tests/CursorPositionCalculatorSpecification.cs

using System;

using NUnit.Framework;

using FluentAssertions;



namespace Ncqrs.EventBus.Tests

{

    [TestFixture]

    public class CursorPositionCalculatorSpecification

    {        

        [Test]

        public void When_event_does_not_lengthen_the_sequence()

        {

            var sut = new CursorPositionCalculator(0);

            sut.Append(CreateProcessingEvent(2));



            sut.Count.Should().Be(1);

            sut.SequenceLength.Should().Be(0);

        }        



        [Test]

        public void When_event_lengthens_the_sequence()

        {

            var sut = new CursorPositionCalculator(0);

            sut.Append(CreateProcessingEvent(1));



            sut.Count.Should().Be(1);

            sut.SequenceLength.Should().Be(1);   

        }

        

        [Test]

        public void When_event_fills_gap_in_sequence_sequence_length_is_incremented_by_gap_size()

        {

            var sut = new CursorPositionCalculator(0);

            sut.Append(CreateProcessingEvent(2));

            sut.Append(CreateProcessingEvent(3));

            sut.Append(CreateProcessingEvent(5));



            sut.Append(CreateProcessingEvent(1));



            sut.Count.Should().Be(4);

            sut.SequenceLength.Should().Be(3);            

        }



        [Test]

        public void When_clearing_sequence()

        {

            var sut = new CursorPositionCalculator(0);

            sut.Append(CreateProcessingEvent(1));

            sut.Append(CreateProcessingEvent(2));

            sut.Append(CreateProcessingEvent(4));



            sut.ClearSequence();



            sut.Count.Should().Be(1);

            sut.SequenceLength.Should().Be(0);

        }        



        private static IProcessingElement CreateProcessingEvent(int sequence)

        {

            return new FakeProcessingElement {SequenceNumber = sequence};

        }

    }

}