diff --git a/Octokit.Tests/Reactive/ObservablePullRequestReviewCommentsClientTests.cs b/Octokit.Tests/Reactive/ObservablePullRequestReviewCommentsClientTests.cs
index f1628e2c..600653c4 100644
--- a/Octokit.Tests/Reactive/ObservablePullRequestReviewCommentsClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservablePullRequestReviewCommentsClientTests.cs
@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using NSubstitute;
 using Octokit.Internal;
 using Octokit.Reactive;
+using System.Reactive.Threading.Tasks;
 using Octokit.Tests.Helpers;
 using Xunit;
 
@@ -81,12 +82,12 @@ namespace Octokit.Tests.Reactive
                 var gitHubClient = Substitute.For<IGitHubClient>();
                 var client = new ObservablePullRequestReviewCommentsClient(gitHubClient);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAll(null, "name", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAll("", "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAll("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAll("owner", "", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAll(null, null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAll("", "", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAll(null, "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAll("", "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAll("owner", null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAll("owner", "", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAll(null, null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAll("", "", 1).ToTask());
             }
         }
 
@@ -232,11 +233,11 @@ namespace Octokit.Tests.Reactive
 
                 var request = new PullRequestReviewCommentRequest();
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAllForRepository(null, "name", request));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAllForRepository("", "name", request));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAllForRepository("owner", null, request));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAllForRepository("owner", "", request));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAllForRepository("owner", "name", null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAllForRepository(null, "name", request).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAllForRepository("", "name", request).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAllForRepository("owner", null, request).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAllForRepository("owner", "", request).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetAllForRepository("owner", "name", null).ToTask());
             }
         }
 
@@ -258,12 +259,12 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservablePullRequestReviewCommentsClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetComment(null, "name", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetComment("", "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetComment("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetComment("owner", "", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetComment(null, null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetComment("", "", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetComment(null, "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetComment("", "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetComment("owner", null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetComment("owner", "", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetComment(null, null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetComment("", "", 1).ToTask());
             }
         }
 
@@ -295,11 +296,11 @@ namespace Octokit.Tests.Reactive
 
                 var comment = new PullRequestReviewCommentCreate(body, commitId, path, position);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Create(null, "name", 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Create("", "name", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Create("owner", null, 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Create("owner", "", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Create("owner", "name", 1, null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Create(null, "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Create("", "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Create("owner", null, 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Create("owner", "", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Create("owner", "name", 1, null).ToTask());
             }
         }
 
@@ -329,11 +330,11 @@ namespace Octokit.Tests.Reactive
 
                 var comment = new PullRequestReviewCommentReplyCreate(body, inReplyTo);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.CreateReply(null, "name", 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.CreateReply("", "name", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.CreateReply("owner", null, 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.CreateReply("owner", "", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.CreateReply("owner", "name", 1, null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.CreateReply(null, "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.CreateReply("", "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.CreateReply("owner", null, 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.CreateReply("owner", "", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.CreateReply("owner", "name", 1, null).ToTask());
             }
         }
 
@@ -362,11 +363,11 @@ namespace Octokit.Tests.Reactive
 
                 var comment = new PullRequestReviewCommentEdit(body);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Edit(null, "name", 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Edit("", "name", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Edit("owner", null, 1, comment));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Edit("owner", "", 1, comment));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Edit("owner", "name", 1, null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Edit(null, "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Edit("", "name", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Edit("owner", null, 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Edit("owner", "", 1, comment).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Edit("owner", "name", 1, null).ToTask());
             }
         }
 
@@ -389,10 +390,10 @@ namespace Octokit.Tests.Reactive
                 var gitHubClient = Substitute.For<IGitHubClient>();
                 var client = new ObservablePullRequestReviewCommentsClient(gitHubClient);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Delete(null, "name", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Delete("", "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Delete("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Delete("owner", "", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Delete(null, "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Delete("", "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Delete("owner", null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Delete("owner", "", 1).ToTask());
             }
         }
     }
diff --git a/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs b/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
index e4a2c010..68626854 100644
--- a/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reactive.Linq;
+using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
 using NSubstitute;
 using Octokit.Internal;
@@ -31,10 +32,10 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservablePullRequestsClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Get(null, "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Get("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Get(null, "", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Get("", null, 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Get(null, "name", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Get("owner", null, 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Get(null, "", 1).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Get("", null, 1).ToTask());
             }
         }
 
@@ -173,16 +174,16 @@ namespace Octokit.Tests.Reactive
                 var gitHubClient = Substitute.For<IGitHubClient>();
                 var client = new ObservablePullRequestsClient(gitHubClient);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create(null, "name", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentException>(async () => await
-                    client.Create("", "name", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create("owner", null, new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentException>(async () => await
-                    client.Create("owner", "", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create("owner", "name", null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create(null, "name", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() =>
+                    client.Create("", "name", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create("owner", null, new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() =>
+                    client.Create("owner", "", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create("owner", "name", null).ToTask());
             }
         }
 
@@ -206,16 +207,16 @@ namespace Octokit.Tests.Reactive
                 var gitHubClient = Substitute.For<IGitHubClient>();
                 var client = new ObservablePullRequestsClient(gitHubClient);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create(null, "name", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentException>(async () => await
-                    client.Create("", "name", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create("owner", null, new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentException>(async () => await
-                    client.Create("owner", "", new NewPullRequest("title", "ref", "ref2")));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
-                    client.Create("owner", "name", null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create(null, "name", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() =>
+                    client.Create("", "name", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create("owner", null, new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() =>
+                    client.Create("owner", "", new NewPullRequest("title", "ref", "ref2")).ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
+                    client.Create("owner", "name", null).ToTask());
             }
         }
 
@@ -239,11 +240,11 @@ namespace Octokit.Tests.Reactive
                 var connection = Substitute.For<IApiConnection>();
                 var client = new PullRequestsClient(connection);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
                     client.Merge(null, "name", 42, new MergePullRequest { Message = "message" }));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
                     client.Merge("owner", null, 42, new MergePullRequest { Message = "message" }));
-                await AssertEx.Throws<ArgumentNullException>(async () => await
+                await Assert.ThrowsAsync<ArgumentNullException>(() =>
                     client.Merge("owner", "name", 42, null));
             }
         }
@@ -267,10 +268,10 @@ namespace Octokit.Tests.Reactive
                 var connection = Substitute.For<IApiConnection>();
                 var client = new PullRequestsClient(connection);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Merged(null, "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Merged("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Merged(null, "", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Merged("", null, 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Merged(null, "name", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Merged("owner", null, 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Merged(null, "", 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Merged("", null, 1));
             }
         }
 
@@ -306,10 +307,10 @@ namespace Octokit.Tests.Reactive
                 var connection = Substitute.For<IApiConnection>();
                 var client = new PullRequestsClient(connection);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Commits(null, "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Commits("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Commits(null, "", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Commits("", null, 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Commits(null, "name", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Commits("owner", null, 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Commits(null, "", 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Commits("", null, 1));
             }
         }
 
@@ -345,10 +346,10 @@ namespace Octokit.Tests.Reactive
                 var connection = Substitute.For<IApiConnection>();
                 var client = new PullRequestsClient(connection);
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Files(null, "name", 1));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Files("owner", null, 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Files("", "name", 1));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Files("owner", "", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Files(null, "name", 1));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Files("owner", null, 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Files("", "name", 1));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Files("owner", "", 1));
             }
         }
         public class TheCtor