SystemExtensions/SystemExtensions.Tests/Extensions/OptionalTests.cs

using FluentAssertions;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace System.Extensions.Tests;

[TestClass]
public class OptionalTests
{
    [TestMethod]
    public void SomeValueShouldEqualOptional()
    {
        var value = string.Empty;
        var optional = value.ToOptional();

        Assert.IsTrue(optional.Equals(value));
    }

    [TestMethod]
    public void OptionalFromNullShouldNotEqual()
    {
        object value = null;
        var optional = value.ToOptional();

        Assert.IsFalse(optional.Equals(value));
    }

    [TestMethod]
    public void OptionalFromValueShouldBeSome()
    {
        var optional = Optional.FromValue<object>(new object());

        optional.DoAny(
            onNone: () => throw new InvalidOperationException());
    }

    [TestMethod]
    public void OptionalFromNullShouldBeNone()
    {
        var optional = Optional.FromValue<object>(null);

        optional.DoAny(
            onSome: _ => throw new InvalidOperationException());
    }

    [TestMethod]
    public void DoShouldExecute()
    {
        var optional = Optional.FromValue(string.Empty);
        var nullOptional = Optional.FromValue<string>(null);

        optional.Do(
            onSome: _ => { },
            onNone: () => throw new InvalidOperationException());

        nullOptional.Do(
            onSome: _ => throw new InvalidOperationException(),
            onNone: () => { });
    }

    [TestMethod]
    public void DoAnyShouldExecute()
    {
        var optional = Optional.FromValue(string.Empty);
        var nullOptional = Optional.FromValue<string>(null);

        optional.DoAny(
            onNone: () => throw new InvalidOperationException());

        nullOptional.DoAny(
            onSome: _ => throw new InvalidOperationException());
    }

    [TestMethod]
    public void SwitchShouldExecute()
    {
        var optional = Optional.FromValue(string.Empty);
        var nullOptional = Optional.FromValue<string>(null);

        var newValue = optional.Switch(
            onSome: _ => string.Empty,
            onNone: () => throw new InvalidOperationException())
            .ExtractValue();

        var newNullValue = nullOptional.Switch<string>(
            onSome: _ => throw new InvalidOperationException(),
            onNone: () => null)
            .ExtractValue();

        newValue.Should().Be(string.Empty);
        newNullValue.Should().Be(null);
    }

    [TestMethod]
    public void SwitchAnyShouldExecute()
    {
        var optional = Optional.FromValue(string.Empty);
        var nullOptional = Optional.FromValue<string>(null);

        var newValue = optional.SwitchAny(
            onSome: _ => string.Empty)
            .ExtractValue();

        var newNullValue = nullOptional.SwitchAny<string>(
            onNone: () => null)
            .ExtractValue();

        newValue.Should().Be(string.Empty);
        newNullValue.Should().Be(null);
    }
}