Add Unit Tests.

test/DotNetCore.CAP.Test/ConsumerServiceSelectorTest.cs

+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading.Tasks;
+using DotNetCore.CAP.Abstractions;
+using DotNetCore.CAP.Internal;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace DotNetCore.CAP.Test
+{
+    public class ConsumerServiceSelectorTest
+    {
+
+        private IServiceProvider _provider;
+
+        public ConsumerServiceSelectorTest()
+        {
+            var services = new ServiceCollection();
+            //services.AddSingleton<IConsumerServiceSelector, DefaultConsumerServiceSelector>();
+            services.AddScoped<IFooTest, CandidatesFooTest>();
+            services.AddScoped<IBarTest, CandidatesBarTest>();
+            services.AddLogging();
+            services.AddCap();
+            _provider = services.BuildServiceProvider();
+        }
+
+        [Fact]
+        public void CanFindAllConsumerService()
+        {
+            var selector = _provider.GetRequiredService<IConsumerServiceSelector>();
+            var candidates = selector.SelectCandidates(_provider);
+
+            Assert.Equal(2, candidates.Count);
+        }
+
+        [Fact]
+        public void CanFindSpecifiedTopic()
+        {
+            var selector = _provider.GetRequiredService<IConsumerServiceSelector>();
+            var candidates = selector.SelectCandidates(_provider);
+            var bestCandidates = selector.SelectBestCandidate("Candidates.Foo", candidates);
+
+            Assert.NotNull(bestCandidates);
+            Assert.NotNull(bestCandidates.MethodInfo);
+            Assert.Equal(bestCandidates.MethodInfo.ReturnType, typeof(Task));
+        }
+    }
+
+    public class CandidatesTopic : TopicAttribute
+    {
+        public CandidatesTopic(string topicName) : base(topicName)
+        {
+        }
+    }
+
+    public interface IFooTest { }
+    public interface IBarTest { }
+
+    public class CandidatesFooTest : IFooTest, IConsumerService
+    {
+        [CandidatesTopic("Candidates.Foo")]
+        public Task GetFoo()
+        {
+            Console.WriteLine("GetFoo() method has bee excuted.");
+            return Task.CompletedTask;
+        }
+
+        [CandidatesTopic("Candidates.Foo2")]
+        public void GetFoo2()
+        {
+            Console.WriteLine("GetFoo2() method has bee excuted.");
+        }
+    }
+
+    public class CandidatesBarTest : IBarTest
+    {
+        [CandidatesTopic("Candidates.Bar")]
+        public Task GetBar()
+        {
+            Console.WriteLine("GetBar() method has bee excuted.");
+            return Task.CompletedTask;
+        }
+
+        [CandidatesTopic("Candidates.Bar2")]
+        public void GetBar2()
+        {
+            Console.WriteLine("GetBar2() method has bee excuted.");
+        }
+    }
+
+}