add SingleOrDefault test

Author: jaredcnance

JsonApiDotNetCoreTests/Data/TestData/TestContext.cs

@@ -0,0 +1,14 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace JsonApiDotNetCoreTests.Data.TestData
+{
+  public class TestContext : DbContext
+  {
+    public TestContext(DbContextOptions options)
+      : base(options)
+    {
+    }
+
+    public virtual DbSet<TodoItem> TodoItems { get; set; }
+  }
+}

JsonApiDotNetCoreTests/Data/TestData/TodoItem.cs

@@ -0,0 +1,8 @@
+namespace JsonApiDotNetCoreTests.Data.TestData
+{
+  public class TodoItem
+  {
+    public int Id { get; set; }
+    public string Name { get; set; }
+  }
+}

JsonApiDotNetCoreTests/Data/UnitTests/GenericDataAccessTests.cs

@@ -0,0 +1,43 @@
+using JsonApiDotNetCoreTests.Data.TestData;
+using Microsoft.EntityFrameworkCore;
+using Moq;
+using Xunit;
+using JsonApiDotNetCore.Data;
+using System.Linq;
+using System;
+using System.Collections.Generic;
+
+namespace JsonApiDotNetCoreTests.Data.UnitTests
+{
+    public class GenericDataAccessTests
+    {
+        [Fact]
+        public void SingleOrDefault_Fetches_SingleItemFromContext()
+        {
+            // arrange
+            var data = new List<TodoItem>
+            {
+                new TodoItem { Id = 1, Name = "AAA" },
+                new TodoItem { Id = 2, Name = "BBB" }
+            }.AsQueryable();
+
+            //var mockSet = new Mock<IQueryable<TodoItem>>();
+            var mockSet = new Mock<DbSet<TodoItem>>();
+            mockSet.As<IQueryable<TodoItem>>().Setup(m => m.Provider).Returns(data.Provider);
+            mockSet.As<IQueryable<TodoItem>>().Setup(m => m.Expression).Returns(data.Expression);
+            mockSet.As<IQueryable<TodoItem>>().Setup(m => m.ElementType).Returns(data.ElementType);
+            mockSet.As<IQueryable<TodoItem>>().Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());
+
+
+            var genericDataAccess = new GenericDataAccess();
+
+            // act
+            var item1 = genericDataAccess.SingleOrDefault<TodoItem>(mockSet.Object, "Id", 1);
+            var item2 = genericDataAccess.SingleOrDefault<TodoItem>(mockSet.Object, "Id", 2);
+
+            // assert
+            Assert.Equal(1, item1.Id);
+            Assert.Equal(2, item2.Id);
+        }
+    }
+}