Add streaming integration test

Author: andrewheard

FirebaseAI/Tests/TestApp/Tests/Integration/GenerateContentIntegrationTests.swift

@@ -489,6 +489,73 @@ struct GenerateContentIntegrationTests {
     #expect(response == expectedResponse)
   }
 
+  @Test(arguments: [
+    (InstanceConfig.vertexAI_v1beta, ModelNames.gemini2FlashPreviewImageGeneration),
+    (InstanceConfig.vertexAI_v1beta_global, ModelNames.gemini2FlashPreviewImageGeneration),
+    (InstanceConfig.vertexAI_v1beta_global, ModelNames.gemini2_5_FlashImagePreview),
+    (InstanceConfig.googleAI_v1beta, ModelNames.gemini2FlashPreviewImageGeneration),
+    (InstanceConfig.googleAI_v1beta, ModelNames.gemini2_5_FlashImagePreview),
+    // Note: The following configs are commented out for easy one-off manual testing.
+    // (InstanceConfig.googleAI_v1beta_staging, ModelNames.gemini2FlashPreviewImageGeneration)
+    // (InstanceConfig.googleAI_v1beta_freeTier, ModelNames.gemini2FlashPreviewImageGeneration),
+    // (
+    //  InstanceConfig.googleAI_v1beta_freeTier_bypassProxy,
+    //  ModelNames.gemini2FlashPreviewImageGeneration
+    // ),
+  ])
+  func generateImageStreaming(_ config: InstanceConfig, modelName: String) async throws {
+    let generationConfig = GenerationConfig(
+      temperature: 0.0,
+      topP: 0.0,
+      topK: 1,
+      responseModalities: [.text, .image]
+    )
+    let safetySettings = safetySettings.filter {
+      // HARM_CATEGORY_CIVIC_INTEGRITY is deprecated in Vertex AI but only rejected when using the
+      // 'gemini-2.0-flash-preview-image-generation' model.
+      $0.harmCategory != .civicIntegrity
+    }
+    let model = FirebaseAI.componentInstance(config).generativeModel(
+      modelName: modelName,
+      generationConfig: generationConfig,
+      safetySettings: safetySettings
+    )
+    let prompt = "Generate an image of a cute cartoon kitten playing with a ball of yarn"
+
+    let stream = try model.generateContentStream(prompt)
+
+    var inlineDataParts = [InlineDataPart]()
+    for try await response in stream {
+      let candidate = try #require(response.candidates.first)
+      let inlineDataPart = candidate.content.parts.first { $0 is InlineDataPart } as? InlineDataPart
+      if let inlineDataPart {
+        inlineDataParts.append(inlineDataPart)
+        let inlineDataPartsViaAccessor = response.inlineDataParts
+        #expect(inlineDataPartsViaAccessor.count == 1)
+        #expect(inlineDataPartsViaAccessor == response.inlineDataParts)
+      }
+      let textPart = candidate.content.parts.first { $0 is TextPart } as? TextPart
+      #expect(
+        inlineDataPart != nil || textPart != nil || candidate.finishReason == .stop,
+        "No text or image found in the candidate"
+      )
+    }
+
+    #expect(inlineDataParts.count == 1)
+    let inlineDataPart = try #require(inlineDataParts.first)
+    #expect(inlineDataPart.mimeType == "image/png")
+    #expect(inlineDataPart.data.count > 0)
+    #if canImport(UIKit)
+      let uiImage = try #require(UIImage(data: inlineDataPart.data))
+      // Gemini 2.0 Flash Experimental returns images sized to fit within a 1024x1024 pixel box but
+      // dimensions may vary depending on the aspect ratio.
+      #expect(uiImage.size.width <= 1024)
+      #expect(uiImage.size.width >= 500)
+      #expect(uiImage.size.height <= 1024)
+      #expect(uiImage.size.height >= 500)
+    #endif // canImport(UIKit)
+  }
+
   // MARK: - App Check Tests
 
   @Test(arguments: InstanceConfig.appCheckNotConfiguredConfigs)