Add unit test for duplicate system references

TestAssets/TestProjects/TestMicrosoftCSharpReference/project.json

@@ -8,7 +8,7 @@
         "NETStandard.Library": "1.5.0-rc2-24008"
       }
     },
-    "dnx451": {
+    "net451": {
       "dependencies": {
         "Microsoft.CSharp": "4.0.1-rc2-24008"
       }

TestAssets/TestProjects/TestMscorlibReference/project.json

@@ -0,0 +1,11 @@
+{
+  "version": "1.0.0-*",
+  "dependencies": {},
+  "frameworks": {
+    "net451": {
+      "frameworkAssemblies": {
+        "mscorlib": ""
+      }
+    }
+  }
+}

TestAssets/TestProjects/TestSystemCoreReference/project.json

@@ -0,0 +1,11 @@
+{
+  "version": "1.0.0-*",
+  "dependencies": {},
+  "frameworks": {
+    "net451": {
+      "frameworkAssemblies": {
+        "System": ""
+      }
+    }
+  }
+}

TestAssets/TestProjects/TestSystemReference/project.json

@@ -0,0 +1,11 @@
+{
+  "version": "1.0.0-*",
+  "dependencies": {},
+  "frameworks": {
+    "net451": {
+      "frameworkAssemblies": {
+        "System.Core": ""
+      }
+    }
+  }
+}

test/Microsoft.DotNet.ProjectModel.Tests/PackageDependencyProviderTests.cs

@@ -42,15 +42,25 @@ namespace Microsoft.DotNet.ProjectModel.Tests
             Assert.Empty(p2.RuntimeAssemblies);
         }
 
-        [Fact]
+        [Theory]
-        public void SingleMicrosoftCSharpReference()
+        [InlineDataAttribute("TestMscorlibReference", true)]
+        [InlineDataAttribute("TestMscorlibReference", false)]
+        [InlineDataAttribute("TestMicrosoftCSharpReference", true)]
+        [InlineDataAttribute("TestMicrosoftCSharpReference", false)]
+        [InlineDataAttribute("TestSystemReference", true)]
+        [InlineDataAttribute("TestSystemReference", false)]
+        [InlineDataAttribute("TestSystemCoreReference", true)]
+        [InlineDataAttribute("TestSystemCoreReference", false)]
+        public void TestDuplicateDefaultDesktopReferences(string sampleName, bool withLockFile)
         {
-            // https://github.com/dotnet/cli/issues/1602
+            var instance = TestAssetsManager.CreateTestInstance(sampleName);
-            var instance = TestAssetsManager.CreateTestInstance("TestMicrosoftCSharpReference")
+            if (withLockFile)
-                                            .WithLockFiles();
+            {
+                instance = instance.WithLockFiles();
+            }
 
             var context = new ProjectContextBuilder().WithProjectDirectory(instance.TestRoot)
-                                                     .WithTargetFramework("dnx451")
+                                                     .WithTargetFramework("net451")
                                                      .Build();
 
             Assert.Equal(4, context.RootProject.Dependencies.Count());