diff --git a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/DocumentTests.cs b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/DocumentTests.cs
index ce725f3e..d7ce4ad1 100644
--- a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/DocumentTests.cs
+++ b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/DocumentTests.cs
@@ -14,7 +14,7 @@
 using Microsoft.OpenApi.Models;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-using Moq;
+using NSubstitute;
 
 using Newtonsoft.Json.Linq;
 using Newtonsoft.Json.Serialization;
@@ -35,8 +35,8 @@ public void Given_Null_When_Instantiated_Then_It_Should_Throw_Exception()
         [TestMethod]
         public void Given_That_When_InitialiseDocument_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var result = doc.InitialiseDocument();
 
@@ -48,8 +48,8 @@ public void Given_That_When_InitialiseDocument_Invoked_Then_It_Should_Return_Res
         [DataRow("hello world")]
         public void Given_Info_When_AddMetadata_Invoked_Then_It_Should_Return_Result(string title)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var info = new OpenApiInfo() { Title = title };
 
@@ -75,18 +75,18 @@ public void Given_Info_When_AddMetadata_Invoked_Then_It_Should_Return_Result(str
         [DataRow("https", "localhost", 47071, "api")]
         public void Given_NoOptions_When_AddServer_Invoked_Then_It_Should_Return_Result(string scheme, string host, int port, string routePrefix)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var ports = new[] { 80, 443 };
             var baseHost = $"{host}{(ports.Contains(port) ? string.Empty : $":{port}")}";
             var url = $"{scheme}://{baseHost}/{routePrefix}".TrimEnd('/');
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(baseHost));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(baseHost));
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix);
+                            .AddServer(req, routePrefix);
 
             result.OpenApiDocument.Servers.Should().HaveCount(1);
             result.OpenApiDocument.Servers.First().Url.Should().Be(url);
@@ -107,21 +107,21 @@ public void Given_NoOptions_When_AddServer_Invoked_Then_It_Should_Return_Result(
         [DataRow("https", "localhost", 47071, "api")]
         public void Given_EmptyOptions_When_AddServer_Invoked_Then_It_Should_Return_Result(string scheme, string host, int port, string routePrefix)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var ports = new[] { 80, 443 };
             var baseHost = $"{host}{(ports.Contains(port) ? string.Empty : $":{port}")}";
             var url = $"{scheme}://{baseHost}/{routePrefix}".TrimEnd('/');
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(baseHost));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(baseHost));
 
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.Servers).Returns(new List<OpenApiServer>());
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.Servers.Returns(new List<OpenApiServer>());
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix, options.Object);
+                            .AddServer(req, routePrefix, options);
 
             result.OpenApiDocument.Servers.Should().HaveCount(1);
             result.OpenApiDocument.Servers.First().Url.Should().Be(url);
@@ -142,23 +142,23 @@ public void Given_EmptyOptions_When_AddServer_Invoked_Then_It_Should_Return_Resu
         [DataRow("https", "localhost", 47071, "api", "helloworld")]
         public void Given_ExtraServers_And_Include_When_AddServer_Invoked_Then_It_Should_Return_Result(string scheme, string host, int port, string routePrefix, string server)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var ports = new[] { 80, 443 };
             var baseHost = $"{host}{(ports.Contains(port) ? string.Empty : $":{port}")}";
             var url = $"{scheme}://{baseHost}/{routePrefix}".TrimEnd('/');
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(baseHost));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(baseHost));
 
             var servers = new List<OpenApiServer>() { new OpenApiServer() { Url = server } };
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.Servers).Returns(servers);
-            options.SetupGet(p => p.ExcludeRequestingHost).Returns(false);
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.Servers.Returns(servers);
+            options.ExcludeRequestingHost.Returns(false);
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix, options.Object);
+                            .AddServer(req, routePrefix, options);
 
             result.OpenApiDocument.Servers.Should().HaveCount(2);
             result.OpenApiDocument.Servers.First().Url.Should().Be(url);
@@ -180,23 +180,23 @@ public void Given_ExtraServers_And_Include_When_AddServer_Invoked_Then_It_Should
         [DataRow("https", "localhost", 47071, "api", "helloworld")]
         public void Given_ExtraServers_And_Exclude_When_AddServer_Invoked_Then_It_Should_Return_Result(string scheme, string host, int port, string routePrefix, string server)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var ports = new[] { 80, 443 };
             var baseHost = $"{host}{(ports.Contains(port) ? string.Empty : $":{port}")}";
             var url = $"{scheme}://{baseHost}/{routePrefix}".TrimEnd('/');
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(baseHost));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(baseHost));
 
             var servers = new List<OpenApiServer>() { new OpenApiServer() { Url = server } };
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.Servers).Returns(servers);
-            options.SetupGet(p => p.ExcludeRequestingHost).Returns(true);
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.Servers.Returns(servers);
+            options.ExcludeRequestingHost.Returns(true);
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix, options.Object);
+                            .AddServer(req, routePrefix, options);
 
             result.OpenApiDocument.Servers.Should().HaveCount(1);
             result.OpenApiDocument.Servers.First().Url.Should().Be(server);
@@ -217,17 +217,17 @@ public void Given_ExtraServers_And_Exclude_When_AddServer_Invoked_Then_It_Should
         [DataRow("https", "localhost:47071", null, "https://localhost:47071")]
         public void Given_NullOptions_When_AddServer_Invoked_Then_It_Should_Return_BaseUrl(string scheme, string host, string routePrefix, string expected)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
 
             var hostString = new HostString(host);
-            req.SetupGet(p => p.Host).Returns(hostString);
+            req.Host.Returns(hostString);
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix, null);
+                            .AddServer(req, routePrefix, null);
 
             result.OpenApiDocument.Servers.Should().HaveCount(1);
             result.OpenApiDocument.Servers.First().Url.Should().Be(expected);
@@ -284,22 +284,22 @@ public void Given_NullOptions_When_AddServer_Invoked_Then_It_Should_Return_BaseU
         [DataRow("https", "localhost:47071", null, false, false, "https://localhost:47071")]
         public void Given_Options_When_AddServer_Invoked_Then_It_Should_Return_BaseUrl(string scheme, string host, string routePrefix, bool forceHttps, bool forceHttp, string expected)
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
 
             var hostString = new HostString(host);
-            req.SetupGet(p => p.Host).Returns(hostString);
+            req.Host.Returns(hostString);
 
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.ForceHttps).Returns(forceHttps);
-            options.SetupGet(p => p.ForceHttp).Returns(forceHttp);
-            options.SetupGet(p => p.Servers).Returns(new List<OpenApiServer>());
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.ForceHttps.Returns(forceHttps);
+            options.ForceHttp.Returns(forceHttp);
+            options.Servers.Returns(new List<OpenApiServer>());
 
             var result = doc.InitialiseDocument()
-                            .AddServer(req.Object, routePrefix, options.Object);
+                            .AddServer(req, routePrefix, options);
 
             result.OpenApiDocument.Servers.Should().HaveCount(1);
             result.OpenApiDocument.Servers.First().Url.Should().Be(expected);
@@ -308,8 +308,8 @@ public void Given_Options_When_AddServer_Invoked_Then_It_Should_Return_BaseUrl(s
         [TestMethod]
         public void Given_Null_When_AddNamingStrategy_Invoked_Then_It_Should_Throw_Exception()
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             Action action = () => doc.AddNamingStrategy(null);
 
@@ -321,8 +321,8 @@ public void Given_That_When_AddNamingStrategy_Invoked_Then_It_Should_Return_Resu
         {
             var field = typeof(Document).GetField("_strategy", BindingFlags.Instance | BindingFlags.NonPublic);
             var strategy = new DefaultNamingStrategy();
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var result = doc.AddNamingStrategy(strategy);
 
@@ -333,8 +333,8 @@ public void Given_That_When_AddNamingStrategy_Invoked_Then_It_Should_Return_Resu
         [TestMethod]
         public void Given_Null_When_AddVisitors_Invoked_Then_It_Should_Throw_Exception()
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             Action action = () => doc.AddVisitors(null);
 
@@ -346,8 +346,8 @@ public void Given_That_When_AddVisitors_Invoked_Then_It_Should_Return_Result()
         {
             var field = typeof(Document).GetField("_collection", BindingFlags.Instance | BindingFlags.NonPublic);
             var collection = new VisitorCollection();
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var result = doc.AddVisitors(collection);
 
@@ -358,8 +358,8 @@ public void Given_That_When_AddVisitors_Invoked_Then_It_Should_Return_Result()
         [TestMethod]
         public void Given_Null_When_ApplyDocumentFilters_Invoked_Then_It_Should_Throw_Exception()
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             Action action = () => doc.ApplyDocumentFilters(null);
 
@@ -369,24 +369,24 @@ public void Given_Null_When_ApplyDocumentFilters_Invoked_Then_It_Should_Throw_Ex
         [TestMethod]
         public void Given_That_When_ApplyDocumentFilters_Invoked_Then_It_Should_Invoke_Each_Filter()
         {
-            var documentFilter = new Mock<IDocumentFilter>();
-            var collection = new DocumentFilterCollection(new List<IDocumentFilter> { documentFilter.Object });
+            var documentFilter = Substitute.For<IDocumentFilter>();
+            var collection = new DocumentFilterCollection(new List<IDocumentFilter> { documentFilter });
             var openApiDocument = new OpenApiDocument();
             var doc = new Document(openApiDocument);
 
-            var req = new Mock<IHttpRequestDataObject>();
+            var req = Substitute.For<IHttpRequestDataObject>();
 
-            doc.AddServer(req.Object, "");
+            doc.AddServer(req, "");
             doc.ApplyDocumentFilters(collection);
 
-            documentFilter.Verify(x => x.Apply(req.Object, openApiDocument), Times.Once());
+            documentFilter.Received(1).Apply(req, openApiDocument);
         }
 
         [TestMethod]
         public async Task Given_VersionAndFormat_When_RenderAsync_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
-            var doc = new Document(helper.Object);
+            var helper = Substitute.For<IDocumentHelper>();
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
                                   .RenderAsync(OpenApiSpecVersion.OpenApi2_0, OpenApiFormat.Json);
@@ -399,12 +399,12 @@ public async Task Given_VersionAndFormat_When_RenderAsync_Invoked_Then_It_Should
         [TestMethod]
         public async Task Given_Metadata_When_RenderAsync_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
+            var helper = Substitute.For<IDocumentHelper>();
 
             var title = "hello world";
             var info = new OpenApiInfo() { Title = title };
 
-            var doc = new Document(helper.Object);
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
                                   .AddMetadata(info)
@@ -418,21 +418,21 @@ public async Task Given_Metadata_When_RenderAsync_Invoked_Then_It_Should_Return_
         [TestMethod]
         public async Task Given_ServerDetails_When_RenderAsync_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
+            var helper = Substitute.For<IDocumentHelper>();
 
             var scheme = "https";
             var host = "localhost";
             var routePrefix = "api";
 
             var url = $"{scheme}://{host}";
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(host));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(host));
 
-            var doc = new Document(helper.Object);
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
-                                  .AddServer(req.Object, routePrefix)
+                                  .AddServer(req, routePrefix)
                                   .RenderAsync(OpenApiSpecVersion.OpenApi2_0, OpenApiFormat.Json);
 
             dynamic json = JObject.Parse(result);
@@ -447,23 +447,23 @@ public async Task Given_ServerDetails_When_RenderAsync_Invoked_Then_It_Should_Re
         [DataRow(true, "fabrikam.com", "contoso.com")]
         public async Task Given_ServerDetails_With_ConfigurationOptions_When_RenderAsync_Invoked_Then_It_Should_Return_Result(bool excludeRequestingHost, string host, string expected)
         {
-            var helper = new Mock<IDocumentHelper>();
+            var helper = Substitute.For<IDocumentHelper>();
 
             var scheme = "https";
             var routePrefix = "api";
 
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(host));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(host));
 
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.ExcludeRequestingHost).Returns(excludeRequestingHost);
-            options.SetupGet(p => p.Servers).Returns(new List<OpenApiServer>() { new OpenApiServer() { Url = $"{scheme}://contoso.com/{routePrefix}" } });
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.ExcludeRequestingHost.Returns(excludeRequestingHost);
+            options.Servers.Returns(new List<OpenApiServer>() { new OpenApiServer() { Url = $"{scheme}://contoso.com/{routePrefix}" } });
 
-            var doc = new Document(helper.Object);
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
-                                  .AddServer(req.Object, routePrefix, options.Object)
+                                  .AddServer(req, routePrefix, options)
                                   .RenderAsync(OpenApiSpecVersion.OpenApi2_0, OpenApiFormat.Json);
 
             dynamic json = JObject.Parse(result);
@@ -476,21 +476,21 @@ public async Task Given_ServerDetails_With_ConfigurationOptions_When_RenderAsync
         [TestMethod]
         public async Task Given_ServerDetails_WithNullRoutePrefix_When_RenderAsync_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
+            var helper = Substitute.For<IDocumentHelper>();
 
             var scheme = "https";
             var host = "localhost";
             string routePrefix = null;
 
             var url = $"{scheme}://{host}";
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(host));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(host));
 
-            var doc = new Document(helper.Object);
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
-                                  .AddServer(req.Object, routePrefix)
+                                  .AddServer(req, routePrefix)
                                   .RenderAsync(OpenApiSpecVersion.OpenApi2_0, OpenApiFormat.Json);
 
             dynamic json = JObject.Parse(result);
@@ -503,21 +503,21 @@ public async Task Given_ServerDetails_WithNullRoutePrefix_When_RenderAsync_Invok
         [TestMethod]
         public async Task Given_ServerDetails_WithEmptyRoutePrefix_When_RenderAsync_Invoked_Then_It_Should_Return_Result()
         {
-            var helper = new Mock<IDocumentHelper>();
+            var helper = Substitute.For<IDocumentHelper>();
 
             var scheme = "https";
             var host = "localhost";
             var routePrefix = string.Empty;
 
             var url = $"{scheme}://{host}";
-            var req = new Mock<IHttpRequestDataObject>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
-            req.SetupGet(p => p.Host).Returns(new HostString(host));
+            var req = Substitute.For<IHttpRequestDataObject>();
+            req.Scheme.Returns(scheme);
+            req.Host.Returns(new HostString(host));
 
-            var doc = new Document(helper.Object);
+            var doc = new Document(helper);
 
             var result = await doc.InitialiseDocument()
-                                  .AddServer(req.Object, routePrefix)
+                                  .AddServer(req, routePrefix)
                                   .RenderAsync(OpenApiSpecVersion.OpenApi2_0, OpenApiFormat.Json);
 
             dynamic json = JObject.Parse(result);
diff --git a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/HttpRequestObjectTests.cs b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/HttpRequestObjectTests.cs
index 6d3db758..11a7e9bb 100644
--- a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/HttpRequestObjectTests.cs
+++ b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/HttpRequestObjectTests.cs
@@ -12,7 +12,7 @@
 using Microsoft.Extensions.Primitives;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-using Moq;
+using NSubstitute;
 
 namespace Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests
 {
@@ -34,20 +34,20 @@ public void Given_Null_Parameter_When_Instantiated_Then_It_Should_Throw_Exceptio
         [DataRow("https", "localhost", 47071, "lorem", "ipsum", "consectetur", "hello world")]
         public void Given_Parameter_When_Instantiated_Then_It_Should_Return_Result(string scheme, string hostname, int port, string key, string value, string authType, string payload)
         {
-            var req = new Mock<HttpRequest>();
-            req.SetupGet(p => p.Scheme).Returns(scheme);
+            var req = Substitute.For<HttpRequest>();
+            req.Scheme.Returns(scheme);
 
             var ports = new[] { 80, 443 };
             var baseHost = $"{hostname}{(ports.Contains(port) ? string.Empty : $":{port}")}";
             var hoststring = new HostString(baseHost);
-            req.SetupGet(p => p.Host).Returns(hoststring);
+            req.Host.Returns(hoststring);
 
             var dict = new Dictionary<string, StringValues>() { { key, new StringValues(value) } };
             var header = new HeaderDictionary(dict);
-            req.SetupGet(p => p.Headers).Returns(header);
+            req.Headers.Returns(header);
 
             var query = new QueryCollection(dict);
-            req.SetupGet(p => p.Query).Returns(query);
+            req.Query.Returns(query);
 
             var identities = new List<ClaimsIdentity>()
             {
@@ -58,13 +58,13 @@ public void Given_Parameter_When_Instantiated_Then_It_Should_Return_Result(strin
             };
             var user = new ClaimsPrincipal(identities);
 
-            req.SetupGet(p => p.HttpContext.User).Returns(user);
+            req.HttpContext.User.Returns(user);
 
             var bytes = Encoding.UTF8.GetBytes(payload);
             var body = new MemoryStream(bytes);
-            req.SetupGet(p => p.Body).Returns(body);
+            req.Body.Returns(body);
 
-            var result = new HttpRequestObject(req.Object);
+            var result = new HttpRequestObject(req);
 
             result.Scheme.Should().Be(scheme);
             result.Host.Value.Should().Be(baseHost);
diff --git a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests.csproj b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests.csproj
index 7f7f5351..ae64dc23 100644
--- a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests.csproj
+++ b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests.csproj
@@ -20,9 +20,9 @@
     </PackageReference>
     <PackageReference Include="FluentAssertions" Version="6.8.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.4.1" />
-    <PackageReference Include="Moq" Version="4.18.3" />
     <PackageReference Include="MSTest.TestAdapter" Version="3.0.0" />
     <PackageReference Include="MSTest.TestFramework" Version="3.0.0" />
+    <PackageReference Include="NSubstitute" Version="5.0.0" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiHttpTriggerContextTests.cs b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiHttpTriggerContextTests.cs
index df19f50b..76586af2 100644
--- a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiHttpTriggerContextTests.cs
+++ b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiHttpTriggerContextTests.cs
@@ -15,7 +15,7 @@
 using Microsoft.OpenApi;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-using Moq;
+using NSubstitute;
 
 using Newtonsoft.Json.Serialization;
 
@@ -234,7 +234,7 @@ public async Task Given_Type_When_Initiated_Then_It_Should_Return_IsDevelopment(
         public async Task Given_Authorization_When_AuthorizeAsync_Invoked_Then_It_Should_Return_Result()
         {
             var location = new FileInfo(Assembly.GetExecutingAssembly().Location).Directory.FullName;
-            var req = new Mock<IHttpRequestDataObject>();
+            var req = Substitute.For<IHttpRequestDataObject>();
 
             var res = new OpenApiAuthorizationResult()
             {
@@ -243,16 +243,16 @@ public async Task Given_Authorization_When_AuthorizeAsync_Invoked_Then_It_Should
                 Payload = FakeOpenApiHttpTriggerAuthorization.Payload,
             };
 
-            var auth = new Mock<IOpenApiHttpTriggerAuthorization>();
-            auth.Setup(p => p.AuthorizeAsync(It.IsAny<IHttpRequestDataObject>())).ReturnsAsync(res);
+            var auth = Substitute.For<IOpenApiHttpTriggerAuthorization>();
+            auth.AuthorizeAsync(Arg.Any<IHttpRequestDataObject>()).Returns(res);
 
-            var options = new Mock<IOpenApiConfigurationOptions>();
-            options.SetupGet(p => p.Security).Returns(auth.Object);
+            var options = Substitute.For<IOpenApiConfigurationOptions>();
+            options.Security.Returns(auth);
 
-            var context = new OpenApiHttpTriggerContext(options.Object);
+            var context = new OpenApiHttpTriggerContext(options);
 
             var result = await context.SetApplicationAssemblyAsync(location, false)
-                                      .AuthorizeAsync(req.Object);
+                                      .AuthorizeAsync(req);
 
             result.StatusCode.Should().Be(FakeOpenApiHttpTriggerAuthorization.StatusCode);
             result.ContentType.Should().Be(FakeOpenApiHttpTriggerAuthorization.ContentType);
diff --git a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiTriggerFunctionProviderTests.cs b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiTriggerFunctionProviderTests.cs
index 139047e4..54d5350b 100644
--- a/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiTriggerFunctionProviderTests.cs
+++ b/test/Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests/OpenApiTriggerFunctionProviderTests.cs
@@ -9,7 +9,7 @@
 using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Enums;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-using Moq;
+using NSubstitute;
 
 namespace Microsoft.Azure.WebJobs.Extensions.OpenApi.Tests
 {
@@ -29,10 +29,10 @@ public void Given_Null_When_Instantiated_Then_It_Should_Throw_Exception()
         [DataRow(false, 4)]
         public async Task Given_HideSwaggerUI_When_GetFunctionMetadataAsync_Invoked_Then_It_Should_Return_Result(bool hideSwaggerUI, int expected)
         {
-            var settings = new Mock<OpenApiSettings>();
-            settings.SetupGet(p => p.HideSwaggerUI).Returns(hideSwaggerUI);
+            var settings = Substitute.For<OpenApiSettings>();
+            settings.HideSwaggerUI.Returns(hideSwaggerUI);
 
-            var provider = new OpenApiTriggerFunctionProvider(settings.Object);
+            var provider = new OpenApiTriggerFunctionProvider(settings);
 
             var result = await provider.GetFunctionMetadataAsync().ConfigureAwait(false);
 
@@ -44,10 +44,10 @@ public async Task Given_HideSwaggerUI_When_GetFunctionMetadataAsync_Invoked_Then
         [DataRow(false, 4)]
         public async Task Given_HideDocument_When_GetFunctionMetadataAsync_Invoked_Then_It_Should_Return_Result(bool hideDocument, int expected)
         {
-            var settings = new Mock<OpenApiSettings>();
-            settings.SetupGet(p => p.HideDocument).Returns(hideDocument);
+            var settings = Substitute.For<OpenApiSettings>();
+            settings.HideDocument.Returns(hideDocument);
 
-            var provider = new OpenApiTriggerFunctionProvider(settings.Object);
+            var provider = new OpenApiTriggerFunctionProvider(settings);
 
             var result = await provider.GetFunctionMetadataAsync().ConfigureAwait(false);
 
@@ -61,16 +61,16 @@ public async Task Given_HideDocument_When_GetFunctionMetadataAsync_Invoked_Then_
         [DataRow(OpenApiAuthLevelType.Function, OpenApiAuthLevelType.Function)]
         public async Task Given_AuthLevel_When_GetFunctionMetadataAsync_Invoked_Then_It_Should_Return_Result(OpenApiAuthLevelType authLevelDoc, OpenApiAuthLevelType authLevelUI)
         {
-            var authLevelSettings = new Mock<OpenApiAuthLevelSettings>();
-            authLevelSettings.SetupGet(p => p.Document).Returns(authLevelDoc);
-            authLevelSettings.SetupGet(p => p.UI).Returns(authLevelUI);
+            var authLevelSettings = Substitute.For<OpenApiAuthLevelSettings>();
+            authLevelSettings.Document.Returns(authLevelDoc);
+            authLevelSettings.UI.Returns(authLevelUI);
 
-            var settings = new Mock<OpenApiSettings>();
-            settings.SetupGet(p => p.HideSwaggerUI).Returns(false);
-            settings.SetupGet(p => p.HideDocument).Returns(false);
-            settings.SetupGet(p => p.AuthLevel).Returns(authLevelSettings.Object);
+            var settings = Substitute.For<OpenApiSettings>();
+            settings.HideSwaggerUI.Returns(false);
+            settings.HideDocument.Returns(false);
+            settings.AuthLevel.Returns(authLevelSettings);
 
-            var provider = new OpenApiTriggerFunctionProvider(settings.Object);
+            var provider = new OpenApiTriggerFunctionProvider(settings);
 
             var result = await provider.GetFunctionMetadataAsync().ConfigureAwait(false);