Add test for no mocks declared exception

* Add a check for `PrimaryHandler` being null in the `MockClientHandler` class.
* Throw a new exception with the message "no mocks were provided" if `PrimaryHandler` is null.

---

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Author: jkone27

.devcontainer/devcontainer.json

@@ -0,0 +1,6 @@
+{
+  "tasks": {
+    "test": "dotnet test",
+    "build": "dotnet build"
+  }
+}

ApiStub.FSharp/CE.fs

@@ -199,4 +199,23 @@ module CE =
                     |> ignore
             )
 
-                    
+    type MockClientHandler(handler : HttpMessageHandler, methods, templateMatcher: TemplateMatcher, responseStubber) = 
+        inherit DelegatingHandler(handler)
+
+        override this.SendAsync(request, token) =
+            let wrappedBase = new AsyncCallableHandler(base.InnerHandler) 
+            task {
+                let routeDict = new RouteValueDictionary()
+                if methods |> Array.contains(request.Method) |> not then
+                    return! wrappedBase.CallSendAsync(request, token)
+                else if templateMatcher.TryMatch(request.RequestUri.AbsolutePath |> PathString, routeDict) |> not then
+                    return! wrappedBase.CallSendAsync(request, token)
+                else
+                    if base.InnerHandler = null then
+                        raise (InvalidOperationException("no mocks were provided"))
+                    // HTTP response stubbing happens here, the request has matched, go on with the stub
+                    let! (expected : HttpResponseMessage) = responseStubber request routeDict
+                    // reattach original request!!!
+                    expected.RequestMessage <- request
+                    return expected
+            }

test/ApiStub.FSharp.Tests.fsproj

@@ -9,6 +9,7 @@
     <Compile Include="BDDTests.fs" />
     <Compile Include="BuilderExtensionsTests.fs" />
     <Compile Include="StubberyTests.fs" />
+    <Compile Include="Issues.fs" />
     <Content Include="swagger.json" />
   </ItemGroup>
   <ItemGroup>
@@ -34,4 +35,4 @@
   <ItemGroup>
     <PackageReference Update="FSharp.Core" Version="6.0.3" />
   </ItemGroup>
-</Project>
+</Project>

test/Issues.fs

@@ -0,0 +1,44 @@
+namespace ApiStub.FSharp.Tests
+
+open Xunit
+open fsharpintegrationtests
+open Microsoft.AspNetCore.Mvc.Testing
+open Microsoft.Extensions.DependencyInjection
+open Microsoft.AspNetCore.Hosting
+open SwaggerProvider
+open System.Threading.Tasks
+open System.Net.Http
+open System
+open Microsoft.AspNetCore.TestHost
+open Microsoft.Extensions.Http
+open Microsoft.AspNetCore.Routing.Template
+open Microsoft.AspNetCore.Routing.Patterns
+open Microsoft.AspNetCore.Routing
+open System.Net
+open System.Text.Json
+open Microsoft.AspNetCore.Http
+open System.Net.Http.Json
+open Swensen.Unquote
+open ApiStub.FSharp.CE
+open ApiStub.FSharp.BuilderExtensions
+open ApiStub.FSharp.HttpResponseHelpers
+open ApiStub.FSharp
+open ApiStub.FSharp.BDD
+open HttpResponseMessageExtensions
+open Xunit.Abstractions
+
+module IssuesTests =
+
+    let testce = new CE.TestClient<Startup>()
+
+    [<Fact>]
+    let ``test_no_mocks_declared_throws_exception`` () =
+        task {
+            let factory = testce.GetFactory()
+            let client = factory.CreateClient()
+
+            let! response = client.GetAsync("/Hello")
+            Assert.False(response.IsSuccessStatusCode)
+            let! responseString = response.Content.ReadAsStringAsync()
+            Assert.Contains("no mocks were provided", responseString)
+        }