Add public API tests for GenerateContentResponse (google-gemini#133)

Author: andrewheard

Sources/GoogleAI/GenerateContentResponse.swift

@@ -51,7 +51,7 @@ public struct GenerateContentResponse {
   }
 
   /// Initializer for SwiftUI previews or tests.
-  public init(candidates: [CandidateResponse], promptFeedback: PromptFeedback?) {
+  public init(candidates: [CandidateResponse], promptFeedback: PromptFeedback? = nil) {
     self.candidates = candidates
     self.promptFeedback = promptFeedback
   }

Tests/GoogleAITests/GoogleAITests.swift

@@ -149,6 +149,18 @@ final class GoogleGenerativeAITests: XCTestCase {
     _ = genAI.startChat(history: [ModelContent(parts: "abc")])
   }
 
+  // Public API tests for GenerateContentResponse.
+  func generateContentResponseAPI() {
+    let response = GenerateContentResponse(candidates: [])
+
+    let _: [CandidateResponse] = response.candidates
+    let _: PromptFeedback? = response.promptFeedback
+
+    // Computed Properties
+    let _: String? = response.text
+    let _: [FunctionCall] = response.functionCalls
+  }
+
   // Result builder alternative
 
   /*