Fix(test): Improve write-file and editCorrector test suites

- Enhanced  by:
  - Mocking  and  utilities (, ) to allow for more focused unit testing of .
  - Adding comprehensive tests for the private  method, covering new and existing file scenarios, as well as error handling.
  - Expanding tests for  and  to verify behavior with the new content correction logic, including diff generation and directory creation.
- Refined  by:
  - Introducing robust mocking for  and its methods (, , ) to simulate LLM interactions accurately.
  - Adding extensive test scenarios for , categorized by how  matches and how  is processed, including direct matches, unescaping, and LLM-based corrections.
  - Including tests for edge cases like no matches or multiple matches.
  - Adding a  utility for better test isolation.

Final fix for https://github.com/google-gemini/gemini-cli/issues/484

packages/server/src/utils/editCorrector.test.ts

@@ -4,44 +4,68 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { describe, it, expect } from 'vitest';
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import { vi, describe, it, expect, beforeEach, type Mocked } from 'vitest';
+
+// MOCKS
+let callCount = 0;
+const mockResponses: any[] = [];
+
+let mockGenerateJson: any;
+let mockStartChat: any;
+let mockSendMessageStream: any;
+
+vi.mock('../core/client.js', () => ({
+  GeminiClient: vi.fn().mockImplementation(function (
+    this: any,
+    _config: Config,
+  ) {
+    this.generateJson = (...params: any[]) => mockGenerateJson(...params); // Corrected: use mockGenerateJson
+    this.startChat = (...params: any[]) => mockStartChat(...params); // Corrected: use mockStartChat
+    this.sendMessageStream = (...params: any[]) =>
+      mockSendMessageStream(...params); // Corrected: use mockSendMessageStream
+    return this;
+  }),
+}));
+// END MOCKS
+
 import {
   countOccurrences,
+  ensureCorrectEdit,
   unescapeStringForGeminiBug,
+  resetEditCorrectorCaches_TEST_ONLY,
 } from './editCorrector.js';
+import { GeminiClient } from '../core/client.js';
+import type { Config } from '../config/config.js';
+import { ToolRegistry } from '../tools/tool-registry.js';
+
+vi.mock('../tools/tool-registry.js');
 
 describe('editCorrector', () => {
   describe('countOccurrences', () => {
     it('should return 0 for empty string', () => {
       expect(countOccurrences('', 'a')).toBe(0);
     });
-
     it('should return 0 for empty substring', () => {
       expect(countOccurrences('abc', '')).toBe(0);
     });
-
     it('should return 0 if substring is not found', () => {
       expect(countOccurrences('abc', 'd')).toBe(0);
     });
-
     it('should return 1 if substring is found once', () => {
       expect(countOccurrences('abc', 'b')).toBe(1);
     });
-
     it('should return correct count for multiple occurrences', () => {
       expect(countOccurrences('ababa', 'a')).toBe(3);
       expect(countOccurrences('ababab', 'ab')).toBe(3);
     });
-
     it('should count non-overlapping occurrences', () => {
-      expect(countOccurrences('aaaaa', 'aa')).toBe(2); // Non-overlapping: aa_aa_
-      expect(countOccurrences('ababab', 'aba')).toBe(1); // Non-overlapping: aba_ab -> 1
+      expect(countOccurrences('aaaaa', 'aa')).toBe(2);
+      expect(countOccurrences('ababab', 'aba')).toBe(1);
     });
-
     it('should correctly count occurrences when substring is longer', () => {
       expect(countOccurrences('abc', 'abcdef')).toBe(0);
     });
-
     it('should be case sensitive', () => {
       expect(countOccurrences('abcABC', 'a')).toBe(1);
       expect(countOccurrences('abcABC', 'A')).toBe(1);
@@ -56,62 +80,403 @@ describe('editCorrector', () => {
       expect(unescapeStringForGeminiBug('\\"')).toBe('"');
       expect(unescapeStringForGeminiBug('\\`')).toBe('`');
     });
-
     it('should handle multiple escaped sequences', () => {
       expect(unescapeStringForGeminiBug('Hello\\nWorld\\tTest')).toBe(
         'Hello\nWorld\tTest',
       );
     });
-
     it('should not alter already correct sequences', () => {
       expect(unescapeStringForGeminiBug('\n')).toBe('\n');
       expect(unescapeStringForGeminiBug('Correct string')).toBe(
         'Correct string',
       );
     });
-
     it('should handle mixed correct and incorrect sequences', () => {
       expect(unescapeStringForGeminiBug('\\nCorrect\t\\`')).toBe(
         '\nCorrect\t`',
       );
     });
-
     it('should handle backslash followed by actual newline character', () => {
       expect(unescapeStringForGeminiBug('\\\n')).toBe('\n');
       expect(unescapeStringForGeminiBug('First line\\\nSecond line')).toBe(
         'First line\nSecond line',
       );
     });
-
     it('should handle multiple backslashes before an escapable character', () => {
-      expect(unescapeStringForGeminiBug('\\\\n')).toBe('\n'); // \\n -> \n
-      expect(unescapeStringForGeminiBug('\\\\\\t')).toBe('\t'); // \\\t -> \t
-      expect(unescapeStringForGeminiBug('\\\\\\\\`')).toBe('`'); // \\\\` -> `
+      expect(unescapeStringForGeminiBug('\\\\n')).toBe('\n');
+      expect(unescapeStringForGeminiBug('\\\\\\t')).toBe('\t');
+      expect(unescapeStringForGeminiBug('\\\\\\\\`')).toBe('`');
     });
-
     it('should return empty string for empty input', () => {
       expect(unescapeStringForGeminiBug('')).toBe('');
     });
-
     it('should not alter strings with no targeted escape sequences', () => {
       expect(unescapeStringForGeminiBug('abc def')).toBe('abc def');
-      // \\F and \\S are not targeted escapes, so they should remain as \\F and \\S
       expect(unescapeStringForGeminiBug('C:\\Folder\\File')).toBe(
         'C:\\Folder\\File',
       );
     });
-
     it('should correctly process strings with some targeted escapes', () => {
-      // \\U is not targeted, \\n is.
       expect(unescapeStringForGeminiBug('C:\\Users\\name')).toBe(
         'C:\\Users\name',
       );
     });
-
     it('should handle complex cases with mixed slashes and characters', () => {
       expect(
-        unescapeStringForGeminiBug('\\\\\\nLine1\\\nLine2\\tTab\\\\`Tick\\"'),
+        unescapeStringForGeminiBug('\\\\\\\nLine1\\\nLine2\\tTab\\\\`Tick\\"'),
       ).toBe('\nLine1\nLine2\tTab`Tick"');
     });
   });
+
+  describe('ensureCorrectEdit', () => {
+    let mockGeminiClientInstance: Mocked<GeminiClient>;
+    let mockToolRegistry: Mocked<ToolRegistry>;
+    let mockConfigInstance: Config;
+
+    beforeEach(() => {
+      mockToolRegistry = new ToolRegistry({} as Config) as Mocked<ToolRegistry>;
+      const configParams = {
+        apiKey: 'test-api-key',
+        model: 'test-model',
+        sandbox: false as boolean | string,
+        targetDir: '/test',
+        debugMode: false,
+        question: undefined as string | undefined,
+        fullContext: false,
+        coreTools: undefined as string[] | undefined,
+        toolDiscoveryCommand: undefined as string | undefined,
+        toolCallCommand: undefined as string | undefined,
+        mcpServerCommand: undefined as string | undefined,
+        mcpServers: undefined as Record<string, any> | undefined,
+        userAgent: 'test-agent',
+        userMemory: '',
+        geminiMdFileCount: 0,
+        alwaysSkipModificationConfirmation: false,
+      };
+      mockConfigInstance = {
+        ...configParams,
+        getApiKey: vi.fn(() => configParams.apiKey),
+        getModel: vi.fn(() => configParams.model),
+        getSandbox: vi.fn(() => configParams.sandbox),
+        getTargetDir: vi.fn(() => configParams.targetDir),
+        getToolRegistry: vi.fn(() => mockToolRegistry),
+        getDebugMode: vi.fn(() => configParams.debugMode),
+        getQuestion: vi.fn(() => configParams.question),
+        getFullContext: vi.fn(() => configParams.fullContext),
+        getCoreTools: vi.fn(() => configParams.coreTools),
+        getToolDiscoveryCommand: vi.fn(() => configParams.toolDiscoveryCommand),
+        getToolCallCommand: vi.fn(() => configParams.toolCallCommand),
+        getMcpServerCommand: vi.fn(() => configParams.mcpServerCommand),
+        getMcpServers: vi.fn(() => configParams.mcpServers),
+        getUserAgent: vi.fn(() => configParams.userAgent),
+        getUserMemory: vi.fn(() => configParams.userMemory),
+        setUserMemory: vi.fn((mem: string) => {
+          configParams.userMemory = mem;
+        }),
+        getGeminiMdFileCount: vi.fn(() => configParams.geminiMdFileCount),
+        setGeminiMdFileCount: vi.fn((count: number) => {
+          configParams.geminiMdFileCount = count;
+        }),
+        getAlwaysSkipModificationConfirmation: vi.fn(
+          () => configParams.alwaysSkipModificationConfirmation,
+        ),
+        setAlwaysSkipModificationConfirmation: vi.fn((skip: boolean) => {
+          configParams.alwaysSkipModificationConfirmation = skip;
+        }),
+      } as unknown as Config;
+
+      callCount = 0;
+      mockResponses.length = 0;
+      mockGenerateJson = vi.fn().mockImplementation(() => {
+        const response = mockResponses[callCount];
+        callCount++;
+        if (response === undefined) return Promise.resolve({});
+        return Promise.resolve(response);
+      });
+      mockStartChat = vi.fn();
+      mockSendMessageStream = vi.fn();
+
+      mockGeminiClientInstance = new GeminiClient(
+        mockConfigInstance,
+      ) as Mocked<GeminiClient>;
+      resetEditCorrectorCaches_TEST_ONLY();
+    });
+
+    describe('Scenario Group 1: originalParams.old_string matches currentContent directly', () => {
+      it('Test 1.1: old_string (no literal \\), new_string (escaped by Gemini) -> new_string unescaped', async () => {
+        const currentContent = 'This is a test string to find me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find me',
+          new_string: 'replace with \\"this\\"',
+        };
+        mockResponses.push({
+          corrected_new_string_escaping: 'replace with "this"',
+        });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe('replace with "this"');
+        expect(result.params.old_string).toBe('find me');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 1.2: old_string (no literal \\), new_string (correctly formatted) -> new_string unchanged', async () => {
+        const currentContent = 'This is a test string to find me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find me',
+          new_string: 'replace with this',
+        };
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(0);
+        expect(result.params.new_string).toBe('replace with this');
+        expect(result.params.old_string).toBe('find me');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 1.3: old_string (with literal \\), new_string (escaped by Gemini) -> new_string unchanged (still escaped)', async () => {
+        const currentContent = 'This is a test string to find\\me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find\\me',
+          new_string: 'replace with \\"this\\"',
+        };
+        mockResponses.push({
+          corrected_new_string_escaping: 'replace with "this"',
+        });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe('replace with "this"');
+        expect(result.params.old_string).toBe('find\\me');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 1.4: old_string (with literal \\), new_string (correctly formatted) -> new_string unchanged', async () => {
+        const currentContent = 'This is a test string to find\\me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find\\me',
+          new_string: 'replace with this',
+        };
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(0);
+        expect(result.params.new_string).toBe('replace with this');
+        expect(result.params.old_string).toBe('find\\me');
+        expect(result.occurrences).toBe(1);
+      });
+    });
+
+    describe('Scenario Group 2: originalParams.old_string does NOT match, but unescapeStringForGeminiBug(originalParams.old_string) DOES match', () => {
+      it('Test 2.1: old_string (over-escaped, no intended literal \\), new_string (escaped by Gemini) -> new_string unescaped', async () => {
+        const currentContent = 'This is a test string to find "me".';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find \\"me\\"',
+          new_string: 'replace with \\"this\\"',
+        };
+        mockResponses.push({ corrected_new_string: 'replace with "this"' });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe('replace with "this"');
+        expect(result.params.old_string).toBe('find "me"');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 2.2: old_string (over-escaped, no intended literal \\), new_string (correctly formatted) -> new_string unescaped (harmlessly)', async () => {
+        const currentContent = 'This is a test string to find "me".';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find \\"me\\"',
+          new_string: 'replace with this',
+        };
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(0);
+        expect(result.params.new_string).toBe('replace with this');
+        expect(result.params.old_string).toBe('find "me"');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 2.3: old_string (over-escaped, with intended literal \\), new_string (simple) -> new_string corrected', async () => {
+        const currentContent = 'This is a test string to find \\me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find \\\\me',
+          new_string: 'replace with foobar',
+        };
+        mockResponses.push({
+          corrected_target_snippet: 'find \\me',
+        });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe('replace with foobar');
+        expect(result.params.old_string).toBe('find \\me');
+        expect(result.occurrences).toBe(1);
+      });
+    });
+
+    describe('Scenario Group 3: LLM Correction Path', () => {
+      it('Test 3.1: old_string (no literal \\), new_string (escaped by Gemini), LLM re-escapes new_string -> final new_string is double unescaped', async () => {
+        const currentContent = 'This is a test string to corrected find me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find me',
+          new_string: 'replace with \\\\"this\\\\"',
+        };
+        const llmNewString = 'LLM says replace with "that"';
+        mockResponses.push({ corrected_new_string_escaping: llmNewString });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe(llmNewString);
+        expect(result.params.old_string).toBe('find me');
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 3.2: old_string (with literal \\), new_string (escaped by Gemini), LLM re-escapes new_string -> final new_string is unescaped once', async () => {
+        const currentContent = 'This is a test string to corrected find me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find\\me',
+          new_string: 'replace with \\\\"this\\\\"',
+        };
+        const llmCorrectedOldString = 'corrected find me';
+        const llmNewString = 'LLM says replace with "that"';
+        mockResponses.push({ corrected_target_snippet: llmCorrectedOldString });
+        mockResponses.push({ corrected_new_string: llmNewString });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(2);
+        expect(result.params.new_string).toBe(llmNewString);
+        expect(result.params.old_string).toBe(llmCorrectedOldString);
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 3.3: old_string needs LLM, new_string is fine -> old_string corrected, new_string original', async () => {
+        const currentContent = 'This is a test string to be corrected.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'fiiind me',
+          new_string: 'replace with "this"',
+        };
+        const llmCorrectedOldString = 'to be corrected';
+        mockResponses.push({ corrected_target_snippet: llmCorrectedOldString });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe('replace with "this"');
+        expect(result.params.old_string).toBe(llmCorrectedOldString);
+        expect(result.occurrences).toBe(1);
+      });
+      it('Test 3.4: LLM correction path, correctNewString returns the originalNewString it was passed (which was unescaped) -> final new_string is unescaped', async () => {
+        const currentContent = 'This is a test string to corrected find me.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find me',
+          new_string: 'replace with \\\\"this\\\\"',
+        };
+        const newStringForLLMAndReturnedByLLM = 'replace with "this"';
+        mockResponses.push({
+          corrected_new_string_escaping: newStringForLLMAndReturnedByLLM,
+        });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params.new_string).toBe(newStringForLLMAndReturnedByLLM);
+        expect(result.occurrences).toBe(1);
+      });
+    });
+
+    describe('Scenario Group 4: No Match Found / Multiple Matches', () => {
+      it('Test 4.1: No version of old_string (original, unescaped, LLM-corrected) matches -> returns original params, 0 occurrences', async () => {
+        const currentContent = 'This content has nothing to find.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'nonexistent string',
+          new_string: 'some new string',
+        };
+        mockResponses.push({ corrected_target_snippet: 'still nonexistent' });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(1);
+        expect(result.params).toEqual(originalParams);
+        expect(result.occurrences).toBe(0);
+      });
+      it('Test 4.2: unescapedOldStringAttempt results in >1 occurrences -> returns original params, count occurrences', async () => {
+        const currentContent =
+          'This content has find "me" and also find "me" again.';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'find "me"',
+          new_string: 'some new string',
+        };
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(0);
+        expect(result.params).toEqual(originalParams);
+        expect(result.occurrences).toBe(2);
+      });
+    });
+
+    describe('Scenario Group 5: Specific unescapeStringForGeminiBug checks (integrated into ensureCorrectEdit)', () => {
+      it('Test 5.1: old_string needs LLM to become currentContent, new_string also needs correction', async () => {
+        const currentContent = 'const x = "a\\nbc\\\\"def\\\\"';
+        const originalParams = {
+          file_path: '/test/file.txt',
+          old_string: 'const x = \\\\"a\\\\nbc\\\\\\\\"def\\\\\\\\"',
+          new_string: 'const y = \\\\"new\\\\nval\\\\\\\\"content\\\\\\\\"',
+        };
+        const expectedFinalNewString = 'const y = "new\\nval\\\\"content\\\\"';
+        mockResponses.push({ corrected_target_snippet: currentContent });
+        mockResponses.push({ corrected_new_string: expectedFinalNewString });
+        const result = await ensureCorrectEdit(
+          currentContent,
+          originalParams,
+          mockGeminiClientInstance,
+        );
+        expect(mockGenerateJson).toHaveBeenCalledTimes(2);
+        expect(result.params.old_string).toBe(currentContent);
+        expect(result.params.new_string).toBe(expectedFinalNewString);
+        expect(result.occurrences).toBe(1);
+      });
+    });
+  });
 });