Improve readability and asserts

Author: gericdong

genai/test/textgen-with-txt.test.js

@@ -23,6 +23,8 @@ const sample = require('../text-generation/textgen-with-txt.js');
 describe('textgen-with-txt', async () => {
   it('should generate text content from a text prompt', async () => {
     const output = await sample.generateContent(projectId);
-    assert(output.length > 0);
+    assert(
+      output.length > 0 && output.includes('AI') && output.includes('models')
+    );
   });
 });

genai/text-generation/textgen-with-txt.js

@@ -17,9 +17,12 @@
 // [START googlegenaisdk_textgen_with_txt]
 const {GoogleGenAI} = require('@google/genai');
 
+const GOOGLE_CLOUD_PROJECT = process.env.GOOGLE_CLOUD_PROJECT;
+const GOOGLE_CLOUD_LOCATION = process.env.GOOGLE_CLOUD_LOCATION || 'global';
+
 async function generateContent(
-  projectId = process.env.GOOGLE_CLOUD_PROJECT,
-  location = process.env.GOOGLE_CLOUD_LOCATION || 'global'
+  projectId = GOOGLE_CLOUD_PROJECT,
+  location = GOOGLE_CLOUD_LOCATION
 ) {
   const ai = new GoogleGenAI({
     vertexai: true,