SpdUp/SpdUp.Tests/RelayCommandTests.cs

using SpdUp.Core;

namespace SpdUp.Tests;

/// <summary>
/// Tests for RelayCommand and RelayCommand&lt;T&gt;.
/// </summary>
public class RelayCommandTests
{
    [Fact]
    public void Execute_InvokesAction()
    {
        bool executed = false;
        var cmd = new RelayCommand(() => executed = true);

        cmd.Execute(null);

        Assert.True(executed);
    }

    [Fact]
    public void Execute_WithParameter_InvokesParameterizedAction()
    {
        object? received = null;
        var cmd = new RelayCommand(p => received = p);

        cmd.Execute("test");

        Assert.Equal("test", received);
    }

    [Fact]
    public void CanExecute_DefaultsToTrue()
    {
        var cmd = new RelayCommand(() => { });

        Assert.True(cmd.CanExecute(null));
    }

    [Fact]
    public void CanExecute_RespectsCanExecuteFunc()
    {
        var cmd = new RelayCommand(() => { }, () => false);

        Assert.False(cmd.CanExecute(null));
    }

    [Fact]
    public void CanExecute_ParameterizedPredicate()
    {
        var cmd = new RelayCommand(_ => { }, p => p is "go");

        Assert.True(cmd.CanExecute("go"));
        Assert.False(cmd.CanExecute("stop"));
        Assert.False(cmd.CanExecute(null));
    }

    [Fact]
    public void Constructor_ThrowsOnNullAction()
    {
        Assert.Throws<ArgumentNullException>(() => new RelayCommand((Action<object?>)null!));
    }

    // ── Generic RelayCommand<T> ──────────────────────────────

    [Fact]
    public void Generic_Execute_InvokesWithTypedParameter()
    {
        string? received = null;
        var cmd = new RelayCommand<string>(s => received = s);

        cmd.Execute("hello");

        Assert.Equal("hello", received);
    }

    [Fact]
    public void Generic_CanExecute_DefaultsToTrue()
    {
        var cmd = new RelayCommand<int>(_ => { });

        Assert.True(cmd.CanExecute(42));
    }

    [Fact]
    public void Generic_CanExecute_RespectsFunc()
    {
        var cmd = new RelayCommand<int>(_ => { }, n => n > 0);

        Assert.True(cmd.CanExecute(5));
        Assert.False(cmd.CanExecute(-1));
    }

    [Fact]
    public void Generic_Constructor_ThrowsOnNullAction()
    {
        Assert.Throws<ArgumentNullException>(() => new RelayCommand<string>(null!));
    }
}