ex-col-00-flexarraystring/FlexArray.Test/FlexArrayStringTests.cs

namespace FlexArray.Test;

public class FlexArrayStringTests
{
    // Constructor tests
    [Fact]
    public void Construction_NoSize()
    {
        var array = new FlexArrayString();

        array.Should().NotBeNull();
        array.Count.Should().Be(0, "no items added yet");
        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize, "default capacity");
    }
    
    [Theory]
    [InlineData(0)]
    [InlineData(4)]
    [InlineData(20)]
    [InlineData(100_000)]
    public void Construction_WithSize(int size)
    {
        var array = new FlexArrayString(size);

        array.Should().NotBeNull();
        array.Count.Should().Be(0, "no items added yet");
        array.Capacity.Should().Be(size, "initial capacity set to specified size");
    }

    [Fact]
    public void Construction_WithInvalidSize()
    {
        var array = new FlexArrayString(-5);

        array.Should().NotBeNull();
        array.Count.Should().Be(0);
        array.Capacity.Should().Be(0, "negative size provided => set to 0");
    }
    
    // Add tests
    [Fact]
    public void AddItem_Single()
    {
        var array = new FlexArrayString();

        array.Add("Hello");

        array.Count.Should().Be(1, "one item added");
        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize, "capacity unchanged");
    }
    
    [Fact]
    public void AddItem_Multiple_NoGrowth()
    {
        var array = new FlexArrayString();

        array.Add("Hello");
        array.Add("World");
        array.Add("!");

        array.Count.Should().Be(3, "three items added");
        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize, "no growth required yet");
    }

    [Fact]
    public void AddItem_Multiple_Growth()
    {
        var array = new FlexArrayString();

        void AddItems(int count) 
        {
            for (var i = 0; i < count; i++)
            {
                // random string
                array.Add(Guid.NewGuid().ToString());
            }
        }

        AddItems(FlexArrayString.DefaultStartSize);
        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize);

        AddItems(2);
        array.Capacity.Should().BeGreaterThan(FlexArrayString.DefaultStartSize, "capacity exceeded, had to grow"); 
        array.Count.Should().Be(FlexArrayString.DefaultStartSize + 2);
    }
    
    // Contains tests
    [Fact]
    public void Contains_Success()
    {
        var array = new FlexArrayString();
        array.Add("Goodbye");
        array.Add("World");
        array.Add("!");
        array.Add("bye...");

        array.Contains("!")
             .Should().BeTrue();
    }

    [Fact]
    public void Contains_Success_AfterGrowth()
    {
        var array = new FlexArrayString();
        for (var i = 0; i <= FlexArrayString.DefaultStartSize; i++)
        {
            array.Add(i.ToString());
        }

        array.Contains(array[FlexArrayString.DefaultStartSize - 1])
             .Should().BeTrue();
    }

    [Fact]
    public void Contains_Empty()
    {
        var array = new FlexArrayString();

        array.Contains("Hi!")
             .Should().BeFalse("collection is empty");
    }

    [Fact]
    public void Contains_NotFound()
    {
        var array = new FlexArrayString();
        array.Add("Hello");
        array.Add("World");

        array.Contains("!")
             .Should().BeFalse("not contained in list");
    }
    
    // Indexer tests
    [Fact]
    public void Indexer_Simple()
    {
        var array = new FlexArrayString();
        array.Add("Goodbye World!");

        array[0].Should().Be("Goodbye World!");
    }

    [Fact]
    public void Indexer_Multiple()
    {
        var array = new FlexArrayString();
        for (var i = 0; i < 100; i++)
        {
            array.Add((i+1).ToString());
        }

        array[20].Should().Be("21");
        array[88].Should().Be("89");
    }

    [Theory]
    [InlineData(-1, "negative index")]
    [InlineData(2, "index too high")]
    [InlineData(10, "index too high")]
    public void Indexer_InvalidIndex(int index, string reason)
    {
        var array = new FlexArrayString();
        array.Add("Hello");

        array[index].Should().Be(String.Empty, reason);
    }
    
    [Fact]
    public void Iterate()
    {
        var array = new FlexArrayString();
        for (var i = 0; i < 10; i++)
        {
            array.Add(i.ToString());
        }

        for (var i = 0; i < 10; i++)
        {
            array[i].Should().Be(i.ToString());
        }
    }
}