CliFx/CliFx.Tests/DependencyInjectionSpecs.cs

using CliFx.Exceptions;
using FluentAssertions;
using Xunit;

namespace CliFx.Tests
{
    public partial class DependencyInjectionSpecs
    {
        [Fact]
        public void Default_type_activator_can_initialize_a_command_if_it_has_a_parameterless_constructor()
        {
            // Arrange
            var activator = new DefaultTypeActivator();

            // Act
            var obj = activator.CreateInstance(typeof(WithoutDependenciesCommand));

            // Assert
            obj.Should().BeOfType<WithoutDependenciesCommand>();
        }

        [Fact]
        public void Default_type_activator_cannot_initialize_a_command_if_it_does_not_have_a_parameterless_constructor()
        {
            // Arrange
            var activator = new DefaultTypeActivator();

            // Act & assert
            Assert.Throws<CliFxException>(() =>
                activator.CreateInstance(typeof(WithDependenciesCommand)));
        }

        [Fact]
        public void Delegate_type_activator_can_initialize_a_command_using_a_custom_function()
        {
            // Arrange
            var activator = new DelegateTypeActivator(_ =>
                new WithDependenciesCommand(new DependencyA(), new DependencyB()));

            // Act
            var obj = activator.CreateInstance(typeof(WithDependenciesCommand));

            // Assert
            obj.Should().BeOfType<WithDependenciesCommand>();
        }

        [Fact]
        public void Delegate_type_activator_throws_if_the_underlying_function_returns_null()
        {
            // Arrange
            var activator = new DelegateTypeActivator(_ => null);

            // Act & assert
            Assert.Throws<CliFxException>(() =>
                activator.CreateInstance(typeof(WithDependenciesCommand)));
        }
    }
}