feat(routing): Initialize model routing architecture (#8153)

packages/core/src/config/models.test.ts

@@ -0,0 +1,83 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+  getEffectiveModel,
+  DEFAULT_GEMINI_MODEL,
+  DEFAULT_GEMINI_FLASH_MODEL,
+  DEFAULT_GEMINI_FLASH_LITE_MODEL,
+} from './models.js';
+
+describe('getEffectiveModel', () => {
+  describe('When NOT in fallback mode', () => {
+    const isInFallbackMode = false;
+
+    it('should return the Pro model when Pro is requested', () => {
+      const model = getEffectiveModel(isInFallbackMode, DEFAULT_GEMINI_MODEL);
+      expect(model).toBe(DEFAULT_GEMINI_MODEL);
+    });
+
+    it('should return the Flash model when Flash is requested', () => {
+      const model = getEffectiveModel(
+        isInFallbackMode,
+        DEFAULT_GEMINI_FLASH_MODEL,
+      );
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_MODEL);
+    });
+
+    it('should return the Lite model when Lite is requested', () => {
+      const model = getEffectiveModel(
+        isInFallbackMode,
+        DEFAULT_GEMINI_FLASH_LITE_MODEL,
+      );
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_LITE_MODEL);
+    });
+
+    it('should return a custom model name when requested', () => {
+      const customModel = 'custom-model-v1';
+      const model = getEffectiveModel(isInFallbackMode, customModel);
+      expect(model).toBe(customModel);
+    });
+  });
+
+  describe('When IN fallback mode', () => {
+    const isInFallbackMode = true;
+
+    it('should downgrade the Pro model to the Flash model', () => {
+      const model = getEffectiveModel(isInFallbackMode, DEFAULT_GEMINI_MODEL);
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_MODEL);
+    });
+
+    it('should return the Flash model when Flash is requested', () => {
+      const model = getEffectiveModel(
+        isInFallbackMode,
+        DEFAULT_GEMINI_FLASH_MODEL,
+      );
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_MODEL);
+    });
+
+    it('should HONOR the Lite model when Lite is requested', () => {
+      const model = getEffectiveModel(
+        isInFallbackMode,
+        DEFAULT_GEMINI_FLASH_LITE_MODEL,
+      );
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_LITE_MODEL);
+    });
+
+    it('should HONOR any model with "lite" in its name', () => {
+      const customLiteModel = 'gemini-2.5-custom-lite-vNext';
+      const model = getEffectiveModel(isInFallbackMode, customLiteModel);
+      expect(model).toBe(customLiteModel);
+    });
+
+    it('should downgrade any other custom model to the Flash model', () => {
+      const customModel = 'custom-model-v1-unlisted';
+      const model = getEffectiveModel(isInFallbackMode, customModel);
+      expect(model).toBe(DEFAULT_GEMINI_FLASH_MODEL);
+    });
+  });
+});