Add unit test to ensure changes to SetupContext are correct

Author: GeertvanHorrik

src/Cake.Core.Tests/Unit/SetupContextTests.cs

@@ -0,0 +1,42 @@
+using NSubstitute;
+using Xunit;
+
+namespace Cake.Core.Tests.Unit
+{
+    public sealed class SetupContextTests
+    {
+        public sealed class TheConstructor
+        {
+            [Fact]
+            public void Returns_Empty_Tasks_When_Input_Is_Null()
+            {
+                var cakeContextMock = Substitute.For<ICakeContext>();
+                var cakeTaskInfoMock = Substitute.For<ICakeTaskInfo>();
+
+                // Given, When
+                var result = new SetupContext(cakeContextMock, cakeTaskInfoMock, null);
+
+                // Then
+                Assert.NotNull(result.TasksToExecute);
+                Assert.Empty(result.TasksToExecute);
+            }
+
+            [Fact]
+            public void Returns_Injected_Tasks_When_Input_Is_Not_Null()
+            {
+                var cakeContextMock = Substitute.For<ICakeContext>();
+                var cakeTaskInfoMock = Substitute.For<ICakeTaskInfo>();
+
+                // Given, When
+                var result = new SetupContext(cakeContextMock, cakeTaskInfoMock, new[]
+                {
+                    cakeTaskInfoMock
+                });
+
+                // Then
+                Assert.NotNull(result.TasksToExecute);
+                Assert.Single(result.TasksToExecute);
+            }
+        }
+    }
+}