Fixed issues OkGoDoIt#204.

1. Improved ImageGenerationEndpointTests by introducing ImageSize construction helper method in orther to retain access level of ImageSize constructor.
2. Corrected EndpointBase constructor access level (changed to 'protected') in order to support HttpClientResolutionTests

Author: zeecorleone

OpenAI_API/EndpointBase.cs

@@ -27,7 +27,7 @@ public abstract class EndpointBase
 		/// Constructor of the api endpoint base, to be called from the contructor of any devived classes.  Rather than instantiating any endpoint yourself, access it through an instance of <see cref="OpenAIAPI"/>.
 		/// </summary>
 		/// <param name="api"></param>
-		internal EndpointBase(OpenAIAPI api)
+		protected EndpointBase(OpenAIAPI api)
 		{
 			this._Api = api;
 		}

OpenAI_Tests/ImageGenerationEndpointTests.cs

@@ -51,8 +51,8 @@ public void CreateDALLE2ImageWithUrl(string size)
 			var api = new OpenAI_API.OpenAIAPI();
 
 			Assert.IsNotNull(api.ImageGenerations);
-
-			var results = api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", 2, new ImageSize(size))).Result;
+			
+			var results = api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", 2, ConstructImageSize(size))).Result;
 			Assert.IsNotNull(results);
 			if (results.CreatedUnixTime.HasValue)
 			{
@@ -108,9 +108,9 @@ public void CreateDALLE3ImageWithUrl(string quality, string size)
 		{
 			var api = new OpenAI_API.OpenAIAPI();
 
-			Assert.IsNotNull(api.ImageGenerations);
+            Assert.IsNotNull(api.ImageGenerations);
 
-			var results = api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", OpenAI_API.Models.Model.DALLE3, new ImageSize(size), quality)).Result;
+			var results = api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", OpenAI_API.Models.Model.DALLE3, ConstructImageSize(size), quality)).Result;
 			Assert.IsNotNull(results);
 			if (results.CreatedUnixTime.HasValue)
 			{
@@ -139,9 +139,9 @@ public void BadParameterCombosShouldFail(string model, string quality, string si
 		{
 			var api = new OpenAI_API.OpenAIAPI();
 
-			Assert.IsNotNull(api.ImageGenerations);
+            Assert.IsNotNull(api.ImageGenerations);
 
-			Assert.ThrowsAsync<ArgumentException>(async () => await api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", model, new ImageSize(size), quality)));
+            Assert.ThrowsAsync<ArgumentException>(async () => await api.ImageGenerations.CreateImageAsync(new ImageGenerationRequest("A cyberpunk monkey hacker dreaming of a beautiful bunch of bananas, digital art", model, ConstructImageSize(size), quality)));
 		}
 
 		[Test]
@@ -157,6 +157,17 @@ public void BadNumImagesWithDalle3ShouldFail()
 			Assert.ThrowsAsync<Newtonsoft.Json.JsonSerializationException>(async () => await api.ImageGenerations.CreateImageAsync(req));
 		}
 
+		private ImageSize ConstructImageSize(string size)
+			=> size switch
+			{
+                "256x256" => ImageSize._256,
+                "512x512" => ImageSize._512,
+                "1024x1024" => ImageSize._1024,
+                "1024x1792" => ImageSize._1024x1792,
+                "1792x1024" => ImageSize._1792x1024,
+				_ => ImageSize._256
+            };
+
 
 	}
 }