Feature/adding some re route specific validation tests (#590)

* started refactoring json config validation stack because ive made it crap

* inject validators from DI rather than instanciating, next step mock them

* added some unit tests for specific validators on the train yey

test/Ocelot.UnitTests/Configuration/Validation/FileQoSOptionsFluentValidatorTests.cs

@@ -0,0 +1,106 @@
+using System;
+using FluentValidation.Results;
+using Microsoft.Extensions.DependencyInjection;
+using Moq;
+using Ocelot.Configuration.File;
+using Ocelot.Configuration.Validator;
+using Ocelot.Requester;
+using Shouldly;
+using TestStack.BDDfy;
+using Xunit;
+
+namespace Ocelot.UnitTests.Configuration.Validation
+{
+    public class FileQoSOptionsFluentValidatorTests
+    {
+        private FileQoSOptionsFluentValidator _validator;
+        private ServiceCollection _services;
+        private ValidationResult _result;
+        private FileQoSOptions _qosOptions;
+
+        public FileQoSOptionsFluentValidatorTests()
+        {
+            _services = new ServiceCollection();
+            var provider = _services.BuildServiceProvider();
+            _validator = new FileQoSOptionsFluentValidator(provider);
+        }
+
+        [Fact]
+        public void should_be_valid_as_nothing_set()
+        {
+            this.Given(_ => GivenThe(new FileQoSOptions()))
+                .When(_ => WhenIValidate())
+                .Then(_ => ThenTheResultIsValid())
+                .BDDfy();
+        }
+
+        [Fact]
+        public void should_be_valid_as_qos_delegate_set()
+        {
+            var qosOptions = new FileQoSOptions
+            {
+                TimeoutValue = 1,
+                ExceptionsAllowedBeforeBreaking = 1
+            };
+
+            this.Given(_ => GivenThe(qosOptions))
+                .And(_ => GivenAQosDelegate())
+                .When(_ => WhenIValidate())
+                .Then(_ => ThenTheResultIsValid())
+                .BDDfy();
+        }
+
+        [Fact]
+        public void should_be_invalid_as_no_qos_delegate()
+        {
+            var qosOptions = new FileQoSOptions
+            {
+                TimeoutValue = 1,
+                ExceptionsAllowedBeforeBreaking = 1
+            };
+
+            this.Given(_ => GivenThe(qosOptions))
+                .When(_ => WhenIValidate())
+                .Then(_ => ThenTheResultIsInValid())
+                .And(_ => ThenTheErrorIs())
+                .BDDfy();
+
+        }
+
+        private void ThenTheErrorIs()
+        {
+            _result.Errors[0].ErrorMessage.ShouldBe("Unable to start Ocelot because either a ReRoute or GlobalConfiguration are using QoSOptions but no QosDelegatingHandlerDelegate has been registered in dependency injection container. Are you missing a package like Ocelot.Provider.Polly and services.AddPolly()?");
+        }
+
+        private void ThenTheResultIsInValid()
+        {
+            _result.IsValid.ShouldBeFalse();
+        }
+
+        private void GivenAQosDelegate()
+        {
+            QosDelegatingHandlerDelegate fake = (a, b) =>
+            {
+                return null;
+            };
+            _services.AddSingleton<QosDelegatingHandlerDelegate>(fake);
+            var provider = _services.BuildServiceProvider();
+            _validator = new FileQoSOptionsFluentValidator(provider);
+        }
+
+        private void GivenThe(FileQoSOptions qosOptions)
+        {
+            _qosOptions = qosOptions;
+        }
+
+        private void WhenIValidate()
+        {
+            _result = _validator.Validate(_qosOptions);
+        }
+
+        private void ThenTheResultIsValid()
+        {
+            _result.IsValid.ShouldBeTrue();
+        }
+    }
+}