add Gemini image generation test

Author: Trynax

packages/tests/provider-smoke/gemini-generate-image.test.ts

@@ -0,0 +1,56 @@
+import {
+  createEchoGoogle,
+  GeminiModels,
+} from '@merit-systems/echo-typescript-sdk';
+import { generateText } from 'ai';
+import { beforeAll, describe, expect, it } from 'vitest';
+import {
+  ECHO_APP_ID,
+  assertEnv,
+  baseRouterUrl,
+  getApiErrorDetails,
+  getToken,
+} from './test-helpers';
+
+beforeAll(assertEnv);
+
+const GEMINI_IMAGE_MODELS = [
+  'gemini-2.5-flash-image',
+  'gemini-2.5-flash-image-preview',
+] as const;
+
+describe.concurrent('Gemini generateText with image generation', () => {
+  const google = createEchoGoogle(
+    { appId: ECHO_APP_ID!, baseRouterUrl },
+    getToken
+  );
+
+  for (const model_id of GEMINI_IMAGE_MODELS) {
+    it(`Gemini image ${model_id}`, async () => {
+      try {
+        const result = await generateText({
+          model: google(model_id),
+          prompt: 'Generate a simple blue circle',
+        });
+
+  
+        expect(result).toBeDefined();
+
+
+        const imageFile = result.files?.find(file =>
+          file.mediaType?.startsWith('image/')
+        );
+
+        expect(imageFile).toBeDefined();
+        expect(imageFile?.mediaType).toMatch(/^image\//);
+        expect(imageFile?.base64).toBeDefined();
+        expect(imageFile?.base64?.length).toBeGreaterThan(0);
+      } catch (err) {
+        const details = getApiErrorDetails(err);
+        throw new Error(
+          `[generateText with image] Gemini ${model_id} failed: ${details}`
+        );
+      }
+    });
+  }
+});