test(core): improve testing for API request/response parsing (#21227)

Author: sehoon38

integration-tests/api-resilience.responses

@@ -0,0 +1 @@
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"text":"Part 1. "}],"role":"model"},"index":0}]},{"usageMetadata":{"promptTokenCount":100,"candidatesTokenCount":10,"totalTokenCount":110}},{"candidates":[{"content":{"parts":[{"text":"Part 2."}],"role":"model"},"index":0}],"finishReason":"STOP"}]}

integration-tests/api-resilience.test.ts

@@ -0,0 +1,50 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { TestRig } from './test-helper.js';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+describe('API Resilience E2E', () => {
+  let rig: TestRig;
+
+  beforeEach(() => {
+    rig = new TestRig();
+  });
+
+  afterEach(async () => {
+    await rig.cleanup();
+  });
+
+  it('should not crash when receiving metadata-only chunks in a stream', async () => {
+    await rig.setup('api-resilience-metadata-only', {
+      fakeResponsesPath: join(
+        dirname(fileURLToPath(import.meta.url)),
+        'api-resilience.responses',
+      ),
+      settings: {
+        planSettings: { modelRouting: false },
+      },
+    });
+
+    // Run the CLI with a simple prompt.
+    // The fake responses will provide a stream with a metadata-only chunk in the middle.
+    // We use gemini-3-pro-preview to minimize internal service calls.
+    const result = await rig.run({
+      args: ['hi', '--model', 'gemini-3-pro-preview'],
+    });
+
+    // Verify the output contains text from the normal chunks.
+    // If the CLI crashed on the metadata chunk, rig.run would throw.
+    expect(result).toContain('Part 1.');
+    expect(result).toContain('Part 2.');
+
+    // Verify telemetry event for the prompt was still generated
+    const hasUserPromptEvent = await rig.waitForTelemetryEvent('user_prompt');
+    expect(hasUserPromptEvent).toBe(true);
+  });
+});

packages/core/src/code_assist/server.test.ts

@@ -7,7 +7,14 @@
 import { beforeEach, describe, it, expect, vi, afterEach } from 'vitest';
 import { CodeAssistServer } from './server.js';
 import { OAuth2Client } from 'google-auth-library';
-import { UserTierId, ActionStatus } from './types.js';
+import {
+  UserTierId,
+  ActionStatus,
+  type LoadCodeAssistResponse,
+  type GeminiUserTier,
+  type SetCodeAssistGlobalUserSettingRequest,
+  type CodeAssistGlobalUserSettingResponse,
+} from './types.js';
 import { FinishReason } from '@google/genai';
 import { LlmRole } from '../telemetry/types.js';
 import { logInvalidChunk } from '../telemetry/loggers.js';
@@ -678,6 +685,85 @@ describe('CodeAssistServer', () => {
     expect(response).toEqual(mockResponse);
   });
 
+  it('should call fetchAdminControls endpoint', async () => {
+    const { server } = createTestServer();
+    const mockResponse = { adminControlsApplicable: true };
+    const requestPostSpy = vi
+      .spyOn(server, 'requestPost')
+      .mockResolvedValue(mockResponse);
+
+    const req = { project: 'test-project' };
+    const response = await server.fetchAdminControls(req);
+
+    expect(requestPostSpy).toHaveBeenCalledWith('fetchAdminControls', req);
+    expect(response).toEqual(mockResponse);
+  });
+
+  it('should call getCodeAssistGlobalUserSetting endpoint', async () => {
+    const { server } = createTestServer();
+    const mockResponse: CodeAssistGlobalUserSettingResponse = {
+      freeTierDataCollectionOptin: true,
+    };
+    const requestGetSpy = vi
+      .spyOn(server, 'requestGet')
+      .mockResolvedValue(mockResponse);
+
+    const response = await server.getCodeAssistGlobalUserSetting();
+
+    expect(requestGetSpy).toHaveBeenCalledWith(
+      'getCodeAssistGlobalUserSetting',
+    );
+    expect(response).toEqual(mockResponse);
+  });
+
+  it('should call setCodeAssistGlobalUserSetting endpoint', async () => {
+    const { server } = createTestServer();
+    const mockResponse: CodeAssistGlobalUserSettingResponse = {
+      freeTierDataCollectionOptin: true,
+    };
+    const requestPostSpy = vi
+      .spyOn(server, 'requestPost')
+      .mockResolvedValue(mockResponse);
+
+    const req: SetCodeAssistGlobalUserSettingRequest = {
+      freeTierDataCollectionOptin: true,
+    };
+    const response = await server.setCodeAssistGlobalUserSetting(req);
+
+    expect(requestPostSpy).toHaveBeenCalledWith(
+      'setCodeAssistGlobalUserSetting',
+      req,
+    );
+    expect(response).toEqual(mockResponse);
+  });
+
+  it('should call loadCodeAssist during refreshAvailableCredits', async () => {
+    const { server } = createTestServer();
+    const mockPaidTier = {
+      id: 'test-tier',
+      name: 'tier',
+      availableCredits: [{ creditType: 'G1', creditAmount: '50' }],
+    };
+    const mockResponse = { paidTier: mockPaidTier };
+
+    vi.spyOn(server, 'loadCodeAssist').mockResolvedValue(
+      mockResponse as unknown as LoadCodeAssistResponse,
+    );
+
+    // Initial state: server has a paidTier without availableCredits
+    (server as unknown as { paidTier: GeminiUserTier }).paidTier = {
+      id: 'test-tier',
+      name: 'tier',
+    };
+
+    await server.refreshAvailableCredits();
+
+    expect(server.loadCodeAssist).toHaveBeenCalled();
+    expect(server.paidTier?.availableCredits).toEqual(
+      mockPaidTier.availableCredits,
+    );
+  });
+
   describe('robustness testing', () => {
     it('should not crash on random error objects in loadCodeAssist (isVpcScAffectedUser)', async () => {
       const { server } = createTestServer();
@@ -867,6 +953,46 @@ data: ${jsonString}
       );
     });
 
+    it('should handle malformed JSON within a multi-line data block', async () => {
+      const config = makeFakeConfig();
+      const mockRequest = vi.fn();
+      const client = { request: mockRequest } as unknown as OAuth2Client;
+      const server = new CodeAssistServer(
+        client,
+        'test-project',
+        {},
+        'test-session',
+        UserTierId.FREE,
+        undefined,
+        undefined,
+        config,
+      );
+
+      const { Readable } = await import('node:stream');
+      const mockStream = new Readable({
+        read() {},
+      });
+
+      mockRequest.mockResolvedValue({ data: mockStream });
+
+      const stream = await server.requestStreamingPost('testStream', {});
+
+      setTimeout(() => {
+        mockStream.push('data: {\n');
+        mockStream.push('data: "invalid": json\n');
+        mockStream.push('data: }\n\n');
+        mockStream.push(null);
+      }, 0);
+
+      const results = [];
+      for await (const res of stream) {
+        results.push(res);
+      }
+
+      expect(results).toHaveLength(0);
+      expect(logInvalidChunk).toHaveBeenCalled();
+    });
+
     it('should safely process random response streams in generateContentStream (consumed/remaining credits)', async () => {
       const { mockRequest, client } = createTestServer();
       const testServer = new CodeAssistServer(
@@ -914,5 +1040,79 @@ data: ${jsonString}
       }
       // Should not crash
     });
+
+    it('should be resilient to metadata-only chunks without candidates in generateContentStream', async () => {
+      const { mockRequest, client } = createTestServer();
+      const testServer = new CodeAssistServer(
+        client,
+        'test-project',
+        {},
+        'test-session',
+        UserTierId.FREE,
+      );
+      const { Readable } = await import('node:stream');
+
+      // Chunk 2 is metadata-only, no candidates
+      const streamResponses = [
+        {
+          traceId: '1',
+          response: {
+            candidates: [{ content: { parts: [{ text: 'Hello' }] }, index: 0 }],
+          },
+        },
+        {
+          traceId: '2',
+          consumedCredits: [{ creditType: 'GOOGLE_ONE_AI', creditAmount: '5' }],
+          response: {
+            usageMetadata: { promptTokenCount: 10, totalTokenCount: 15 },
+          },
+        },
+        {
+          traceId: '3',
+          response: {
+            candidates: [
+              { content: { parts: [{ text: ' World' }] }, index: 0 },
+            ],
+          },
+        },
+      ];
+
+      const mockStream = new Readable({
+        read() {
+          for (const resp of streamResponses) {
+            this.push(`data: ${JSON.stringify(resp)}\n\n`);
+          }
+          this.push(null);
+        },
+      });
+      mockRequest.mockResolvedValueOnce({ data: mockStream });
+      vi.spyOn(testServer, 'recordCodeAssistMetrics').mockResolvedValue(
+        undefined,
+      );
+
+      const stream = await testServer.generateContentStream(
+        { model: 'test-model', contents: [] },
+        'user-prompt-id',
+        LlmRole.MAIN,
+      );
+
+      const results = [];
+      for await (const res of stream) {
+        results.push(res);
+      }
+
+      expect(results).toHaveLength(3);
+      expect(results[0].candidates).toHaveLength(1);
+      expect(results[0].candidates?.[0].content?.parts?.[0].text).toBe('Hello');
+
+      // Chunk 2 (metadata-only) should still be yielded but with empty candidates
+      expect(results[1].candidates).toHaveLength(0);
+      expect(results[1].usageMetadata?.promptTokenCount).toBe(10);
+
+      expect(results[2].candidates).toHaveLength(1);
+      expect(results[2].candidates?.[0].content?.parts?.[0].text).toBe(
+        ' World',
+      );
+    });
   });
 });