Added unit test that checks caching query result set with ThenFetchMany statement

Author: illkostinf

src/NHibernate.Test/NHSpecificTest/CachingComplexQuery/Car.cs

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+using System;
+
+namespace NHibernate.Test.NHSpecificTest.CachingComplexQuery
+{
+	public class Car
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+
+		public virtual Person Owner { get; set; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/CachingComplexQuery/Child.cs

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+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.CachingComplexQuery
+{
+	public class Child
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+
+		public virtual Person Parent { get; set; }
+
+		public virtual ISet<Pet> Pets
+		{
+			get => _pets ?? (_pets = new HashSet<Pet>());
+			set => _pets = value;
+		}
+		private ISet<Pet> _pets;
+	}
+}

src/NHibernate.Test/NHSpecificTest/CachingComplexQuery/FixtureByCode.cs

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+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NHibernate.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.CachingComplexQuery
+{
+	/// <summary>
+	/// Fixture using 'by code' mappings
+	/// </summary>
+	/// <remarks>
+	/// This fixture is identical to <see cref="Fixture" /> except the <see cref="Person" /> mapping is performed 
+	/// by code in the GetMappings method, and does not require the <c>Mappings.hbm.xml</c> file. Use this approach
+	/// if you prefer.
+	/// </remarks>
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Person>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.Guid));
+				rc.Property(x => x.Name);
+				rc.Property(x => x.Age);
+				rc.Set(
+					x => x.Children,
+					colMap =>
+					{
+						colMap.Inverse(true);
+						colMap.Cascade(Mapping.ByCode.Cascade.DeleteOrphans);
+						colMap.Cache(c => c.Usage(CacheUsage.ReadWrite));
+					},
+					rel => rel.OneToMany());
+				rc.Set(
+					x => x.Cars,
+					colMap =>
+					{
+						colMap.Inverse(true);
+						colMap.Cascade(Mapping.ByCode.Cascade.DeleteOrphans);
+						colMap.Cache(c => c.Usage(CacheUsage.ReadWrite));
+					},
+					rel => rel.OneToMany());
+				rc.Cache(c => c.Usage(CacheUsage.ReadWrite));
+			});
+			mapper.Class<Child>(ch =>
+			{
+				ch.Id(x => x.Id, m => m.Generator(Generators.Guid));
+				ch.Property(x => x.Name);
+				ch.ManyToOne(c => c.Parent);
+
+				ch.Set(
+					x => x.Pets,
+					colMap =>
+					{
+						colMap.Inverse(true);
+						colMap.Cascade(Mapping.ByCode.Cascade.DeleteOrphans);
+						colMap.Cache(c => c.Usage(CacheUsage.ReadWrite));
+					},
+					rel => rel.OneToMany());
+
+				ch.Cache(c => c.Usage(CacheUsage.ReadWrite));
+			});
+			mapper.Class<Pet>(ch =>
+			{
+				ch.Id(x => x.Id, m => m.Generator(Generators.Guid));
+				ch.Property(x => x.Name);
+				ch.ManyToOne(c => c.Owner);
+
+				ch.Cache(c => c.Usage(CacheUsage.ReadWrite));
+			});
+			mapper.Class<Car>(ch =>
+			{
+				ch.Id(x => x.Id, m => m.Generator(Generators.Guid));
+				ch.Property(x => x.Name);
+				ch.ManyToOne(c => c.Owner);
+
+				ch.Cache(c => c.Usage(CacheUsage.ReadWrite));
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var person = new Person { Name = "Person 1", Age = 18 };
+
+				var car1 = new Car { Name = "Car1", Owner = person };
+				var car2 = new Car { Name = "Car2", Owner = person };
+				session.Save(car1);
+				session.Save(car2);
+				
+				session.Save(person);
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Delete("from Pet");
+				session.Delete("from Child");
+				session.Delete("from Car");
+				session.Delete("from Person");
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void TestQueryCachingWithThenFetchMany()
+		{
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					var query =
+						session
+							.Query<Person>()
+							.FetchMany(p => p.Children)
+								.ThenFetchMany(ch => ch.Pets)
+							.FetchMany(p => p.Cars) as IQueryable<Person>;
+
+					query = query.WithOptions(opt =>
+						opt.SetCacheable(true)
+							.SetCacheMode(CacheMode.Normal)
+							.SetCacheRegion("Long_Cache"));
+
+					query.ToList(); // First time the result will be cached
+					Assert.That(() => query.ToList(), Throws.Nothing); // 
+					transaction.Commit();
+				}
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/CachingComplexQuery/Person.cs

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+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.CachingComplexQuery
+{
+	public class Person
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual int Age { get; set; }
+
+		public virtual ISet<Car> Cars
+		{
+			get => _cars ?? (_cars = new HashSet<Car>());
+			set => _cars = value;
+		}
+		private ISet<Car> _cars;
+
+		public virtual ISet<Child> Children
+		{
+			get => _children ?? (_children = new HashSet<Child>());
+			set => _children = value;
+		}
+		private ISet<Child> _children;
+	}
+}

src/NHibernate.Test/NHSpecificTest/CachingComplexQuery/Pet.cs

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+using System;
+
+namespace NHibernate.Test.NHSpecificTest.CachingComplexQuery
+{
+	public class Pet
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+
+		public virtual Child Owner { get; set; }
+	}
+}