MonoGame.Extended/Source/Tests/MonoGame.Extended.Tests/Particles/EmitterTests.cs

using System;
using Microsoft.Xna.Framework;
using MonoGame.Extended.Particles;
using MonoGame.Extended.Particles.Modifiers;
using MonoGame.Extended.Particles.Profiles;
using NUnit.Framework;

namespace MonoGame.Extended.Tests.Particles
{
    [TestFixture]
    public class EmitterTests
    {
        public class UpdateMethod
        {
            [Test]
            public void WhenThereAreParticlesToExpire_DecreasesActiveParticleCount()
            {
                var subject = new ParticleEmitter(null, 100, TimeSpan.FromSeconds(1), Profile.Point())
                {
                    Parameters = new ParticleReleaseParameters
                    {
                        Quantity = 1
                    }
                };

                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 1);
                    
                subject.Update(2f);
                Assert.AreEqual(subject.ActiveParticles, 0);
            }

            [Test]
            public void WhenThereAreParticlesToExpire_DoesNotPassExpiredParticlesToModifiers()
            {
                var subject = new ParticleEmitter(null, 100, TimeSpan.FromSeconds(1), Profile.Point())
                {
                    Parameters = new ParticleReleaseParameters()
                    {
                        Quantity = 1
                    },
                    Modifiers = new IModifier[] {
                        new AssertionModifier(particle => particle.Age <= 1f)
                    }
                };

                subject.Trigger(new Vector2(0f, 0f));
                subject.Update(0.5f);
                subject.Trigger(new Vector2(0f, 0f));
                subject.Update(0.5f);
                subject.Trigger(new Vector2(0f, 0f));
                subject.Update(0.5f);
            }

            [Test]
            public void WhenThereAreNoActiveParticles_GracefullyDoesNothing()
            {
                var subject = new ParticleEmitter(null, 100, TimeSpan.FromSeconds(1), Profile.Point(), autoTrigger: false);

                subject.Update(0.5f);
                Assert.AreEqual(subject.ActiveParticles, 0);
            }
        }

        public class TriggerMethod
        {
            [Test]
            public void WhenEnoughHeadroom_IncreasesActiveParticlesCountByReleaseQuantity()
            {
                var subject = new ParticleEmitter(null, 100, TimeSpan.FromSeconds(1), Profile.Point())
                {
                    Parameters = new ParticleReleaseParameters
                    {
                        Quantity = 10
                    }
                };
                Assert.AreEqual(subject.ActiveParticles, 0);
                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 10);
            }

            [Test]
            public void WhenNotEnoughHeadroom_IncreasesActiveParticlesCountByRemainingParticles()
            {
                var subject = new ParticleEmitter(null, 15, TimeSpan.FromSeconds(1), Profile.Point())
                {
                    Parameters = new ParticleReleaseParameters
                    {
                        Quantity = 10
                    }
                };

                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 10);
                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 15);
            }

            [Test]
            public void WhenNoRemainingParticles_DoesNotIncreaseActiveParticlesCount()
            {
                var subject = new ParticleEmitter(null, 10, TimeSpan.FromSeconds(1), Profile.Point())
                {
                    Parameters = new ParticleReleaseParameters
                    {
                        Quantity = 10
                    }
                };

                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 10);
                subject.Trigger(new Vector2(0f, 0f));
                Assert.AreEqual(subject.ActiveParticles, 10);
            }
        }

        public class DisposeMethod
        {
            [Test]
            public void IsIdempotent()
            {
                var subject = new ParticleEmitter(null, 10, TimeSpan.FromSeconds(1), Profile.Point());

                subject.Dispose();
                subject.Dispose();
            }
        }
    }
}