Add more tests around IConfiguration/IConfigurationSection support

Author: tsimbalar

test/Serilog.Settings.Configuration.Tests/ConfigurationSettingsTests.cs

@@ -426,28 +426,66 @@ public void SinkWithIConfigurationArguments()
                     ""Using"": [""TestDummies""],
                     ""WriteTo"": [{
                         ""Name"": ""DummyWithConfiguration"",
-                        ""Args"": {""pathFormat"" : ""C:\\"",
-                                   ""configurationSection"" : { ""foo"" : ""bar"" } }
+                        ""Args"": {}
                     }]        
                 }
             }";
 
-            // IConfiguration and IConfigurationSection arguments do not have
-            // default values so they will throw if they are not populated
+            DummyConfigurationSink.Reset();
+            var log = ConfigFromJson(json)
+                .CreateLogger();
 
+            log.Write(Some.InformationEvent());
+
+            Assert.NotNull(DummyConfigurationSink.Configuration);
+        }
+        
+        [Fact]
+        public void SinkWithOptionalIConfigurationArguments()
+        {
+            var json = @"{
+                ""Serilog"": {            
+                    ""Using"": [""TestDummies""],
+                    ""WriteTo"": [{
+                        ""Name"": ""DummyWithOptionalConfiguration"",
+                        ""Args"": {}
+                    }]        
+                }
+            }";
 
             DummyConfigurationSink.Reset();
             var log = ConfigFromJson(json)
                 .CreateLogger();
 
-
             log.Write(Some.InformationEvent());
 
             Assert.NotNull(DummyConfigurationSink.Configuration);
+        }
+        
+        [Fact]
+        public void SinkWithIConfigSectionArguments()
+        {
+            var json = @"{
+                ""Serilog"": {            
+                    ""Using"": [""TestDummies""],
+                    ""WriteTo"": [{
+                        ""Name"": ""DummyWithConfigSection"",
+                        ""Args"": {""configurationSection"" : { ""foo"" : ""bar"" } }
+                    }]        
+                }
+            }";
+
+            DummyConfigurationSink.Reset();
+            var log = ConfigFromJson(json)
+                .CreateLogger();
+
+            log.Write(Some.InformationEvent());
+            
             Assert.NotNull(DummyConfigurationSink.ConfigSection);
             Assert.Equal("bar", DummyConfigurationSink.ConfigSection["foo"]);
         }
 
+
         [Fact]
         public void SinkWithConfigurationBindingArgument()
         {

test/TestDummies/DummyLoggerConfigurationExtensions.cs

@@ -40,11 +40,25 @@ public static LoggerConfiguration DummyRollingFile(
         public static LoggerConfiguration DummyWithConfiguration(
             this LoggerSinkConfiguration loggerSinkConfiguration,
             IConfiguration appConfiguration,
+            LogEventLevel restrictedToMinimumLevel = LevelAlias.Minimum)
+        {
+            return loggerSinkConfiguration.Sink(new DummyConfigurationSink(appConfiguration, null), restrictedToMinimumLevel);
+        }
+
+        public static LoggerConfiguration DummyWithOptionalConfiguration(
+            this LoggerSinkConfiguration loggerSinkConfiguration,
+            IConfiguration appConfiguration = null,
+            LogEventLevel restrictedToMinimumLevel = LevelAlias.Minimum)
+        {
+            return loggerSinkConfiguration.Sink(new DummyConfigurationSink(appConfiguration, null), restrictedToMinimumLevel);
+        }
+
+        public static LoggerConfiguration DummyWithConfigSection(
+            this LoggerSinkConfiguration loggerSinkConfiguration,
             IConfigurationSection configurationSection,
-            string pathFormat,
             LogEventLevel restrictedToMinimumLevel = LevelAlias.Minimum)
         {
-            return loggerSinkConfiguration.Sink(new DummyConfigurationSink(appConfiguration, configurationSection), restrictedToMinimumLevel);
+            return loggerSinkConfiguration.Sink(new DummyConfigurationSink(null, configurationSection), restrictedToMinimumLevel);
         }
 
         public static LoggerConfiguration DummyRollingFile(