Added test for accessing many-to-many data through id, for example: /articles/1/tags (#682)

Author: Bart Koelman

src/Examples/JsonApiDotNetCoreExample/Controllers/TagsController.cs

@@ -0,0 +1,18 @@
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Controllers;
+using JsonApiDotNetCore.Services;
+using JsonApiDotNetCoreExample.Models;
+using Microsoft.Extensions.Logging;
+
+namespace JsonApiDotNetCoreExample.Controllers
+{
+    public class TagsController : JsonApiController<Tag>
+    {
+        public TagsController(
+            IJsonApiOptions jsonApiOptions,
+            IResourceService<Tag> resourceService,
+            ILoggerFactory loggerFactory) 
+            : base(jsonApiOptions, resourceService, loggerFactory)
+        { }
+    }
+}

test/JsonApiDotNetCoreExampleTests/Acceptance/ManyToManyTests.cs

@@ -122,6 +122,45 @@ public async Task Can_Fetch_Many_To_Many_Through_GetById()
             Assert.Equal(tag.Name, tagResponse.Name);
         }
 
+        [Fact]
+        public async Task Can_Fetch_Many_To_Many_Through_Id()
+        {
+            // Arrange
+            var context = _fixture.GetService<AppDbContext>();
+            var article = _articleFaker.Generate();
+            var tag = _tagFaker.Generate();
+            var articleTag = new ArticleTag
+            {
+                Article = article,
+                Tag = tag
+            };
+            context.ArticleTags.Add(articleTag);
+            await context.SaveChangesAsync();
+
+            var route = $"/api/v1/articles/{article.Id}/tags";
+
+            // @TODO - Use fixture
+            var builder = new WebHostBuilder()
+                .UseStartup<Startup>();
+            var server = new TestServer(builder);
+            var client = server.CreateClient();
+
+            // Act
+            var response = await client.GetAsync(route);
+
+            // Assert
+            var body = await response.Content.ReadAsStringAsync();
+            Assert.True(HttpStatusCode.OK == response.StatusCode, $"{route} returned {response.StatusCode} status code with payload: {body}");
+
+            var document = JsonConvert.DeserializeObject<Document>(body);
+            Assert.Single(document.ManyData);
+
+            var tagResponse = _fixture.GetDeserializer().DeserializeList<Tag>(body).Data.First();
+            Assert.NotNull(tagResponse);
+            Assert.Equal(tag.Id, tagResponse.Id);
+            Assert.Equal(tag.Name, tagResponse.Name);
+        }
+
         [Fact]
         public async Task Can_Fetch_Many_To_Many_Through_GetById_Relationship_Link()
         {
@@ -160,7 +199,6 @@ public async Task Can_Fetch_Many_To_Many_Through_GetById_Relationship_Link()
             Assert.Equal(tag.Id, tagResponse.Id);
         }
 
-
         [Fact]
         public async Task Can_Fetch_Many_To_Many_Through_Relationship_Link()
         {