Handle ReadForAsync changes.

Author: Tratcher

test/Microsoft.AspNet.Diagnostics.Tests/ElmMiddlewareTest.cs

@@ -205,8 +205,8 @@ private Mock<HttpContext> GetMockContext(string path)
                 .SetupGet(c => c.Request.Cookies)
                 .Returns(new Mock<IReadableStringCollection>().Object);
             contextMock
-                .Setup(c => c.Request.GetFormAsync(It.IsAny<System.Threading.CancellationToken>()))
-                .Returns(Task.FromResult(new Mock<IReadableStringCollection>().Object));
+                .Setup(c => c.Request.ReadFormAsync(It.IsAny<System.Threading.CancellationToken>()))
+                .Returns(Task.FromResult(new Mock<IFormCollection>().Object));
 
             return contextMock;
         }