/test/NRopes.Tests/ConcateRopeTests.cs

namespace NRopes.Tests {

    using System;

    using System.Collections.Generic;

    using System.Diagnostics;

    using FluentAssertions;

    using Xunit;



    public class ConcateRopeTests : RopeTestsBase {

        private static int Fib(int n) {

            if (n <= 2) return 1;



            return Fib(n - 1) + Fib(n - 2);

        }



        private static ConcateRope CreateRope(int depth, int length) {

            Debug.Assert(depth >= 1);



            var numOfParts = depth + 1;

            var lengthOfParts = length / numOfParts;



            var primitiveRope = new FlatRope(new String(' ', lengthOfParts));



            Rope rope = primitiveRope;

            for (var i = 1; i < numOfParts; i++) {

                if (i < numOfParts - 1) {

                    rope = new ConcateRope(rope, primitiveRope);

                }

                else {

                    var lastRope = new FlatRope(new String(' ', length - rope.Length));

                    rope = new ConcateRope(rope, lastRope);

                }

            }



            var concateRope = rope.As<ConcateRope>();

            Debug.Assert(concateRope.Depth == depth);

            Debug.Assert(concateRope.Length == length);



            return concateRope;

        }



        protected override IEnumerable<Rope> TargetRopes {

            get { yield return new ConcateRope(new FlatRope("A"), new FlatRope("B")); }

        }



        [Fact]

        public void ConstructorShouldThrowIfEitherChildIsNull() {

            new Action(() => new ConcateRope(null, new FlatRope("A")))

                .ShouldThrow<ArgumentNullException>().And

                .ParamName.Should().Be("left");



            new Action(() => new ConcateRope(new FlatRope("B"), null))

                .ShouldThrow<ArgumentNullException>().And

                .ParamName.Should().Be("right");

        }



        [Fact]

        public void SimplePropertiesShouldBeRight() {

            var hwRope = new ConcateRope(new FlatRope("Hello "), new FlatRope("World"));

            hwRope.Depth.Should().Be(1);



            var rope = new ConcateRope(new FlatRope("Say "), hwRope);

            rope.Depth.Should().Be(2);

            rope.Length.Should().Be("Say Hello World".Length);

            rope.ToString().Should().Be("Say Hello World");

        }



        [Fact]

        public void IsBalancedShouldBeFalseForLengthLowerThanFibDepthPlusTwo() {

            CreateRope(1, Fib(3) - 1).IsBalanced.Should().BeFalse();

            CreateRope(2, Fib(4) - 1).IsBalanced.Should().BeFalse();

            CreateRope(5, Fib(7) - 1).IsBalanced.Should().BeFalse();

        }



        [Fact]

        public void IsBalancedShouldBeTrueForLengthGreaterThanOrEqualToFibDepthPlusTwo() {

            CreateRope(1, Fib(3)).IsBalanced.Should().BeTrue();

            CreateRope(2, Fib(4)).IsBalanced.Should().BeTrue();

            CreateRope(5, Fib(7)).IsBalanced.Should().BeTrue();

        }

    }

}