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diff --git a/packages/core/src/tools/read-file.test.ts b/packages/core/src/tools/read-file.test.ts
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+++ b/packages/core/src/tools/read-file.test.ts
@@ -0,0 +1,228 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { vi, describe, it, expect, beforeEach, afterEach, Mock } from 'vitest';
+import { ReadFileTool, ReadFileToolParams } from './read-file.js';
+import * as fileUtils from '../utils/fileUtils.js';
+import path from 'path';
+import os from 'os';
+import fs from 'fs'; // For actual fs operations in setup
+
+// Mock fileUtils.processSingleFileContent
+vi.mock('../utils/fileUtils', async () => {
+  const actualFileUtils =
+    await vi.importActual<typeof fileUtils>('../utils/fileUtils');
+  return {
+    ...actualFileUtils, // Spread actual implementations
+    processSingleFileContent: vi.fn(), // Mock specific function
+  };
+});
+
+const mockProcessSingleFileContent = fileUtils.processSingleFileContent as Mock;
+
+describe('ReadFileTool', () => {
+  let tempRootDir: string;
+  let tool: ReadFileTool;
+  const abortSignal = new AbortController().signal;
+
+  beforeEach(() => {
+    // Create a unique temporary root directory for each test run
+    tempRootDir = fs.mkdtempSync(
+      path.join(os.tmpdir(), 'read-file-tool-root-'),
+    );
+    tool = new ReadFileTool(tempRootDir);
+    mockProcessSingleFileContent.mockReset();
+  });
+
+  afterEach(() => {
+    // Clean up the temporary root directory
+    if (fs.existsSync(tempRootDir)) {
+      fs.rmSync(tempRootDir, { recursive: true, force: true });
+    }
+  });
+
+  describe('validateToolParams', () => {
+    it('should return null for valid params (absolute path within root)', () => {
+      const params: ReadFileToolParams = {
+        path: path.join(tempRootDir, 'test.txt'),
+      };
+      expect(tool.validateToolParams(params)).toBeNull();
+    });
+
+    it('should return null for valid params with offset and limit', () => {
+      const params: ReadFileToolParams = {
+        path: path.join(tempRootDir, 'test.txt'),
+        offset: 0,
+        limit: 10,
+      };
+      expect(tool.validateToolParams(params)).toBeNull();
+    });
+
+    it('should return error for relative path', () => {
+      const params: ReadFileToolParams = { path: 'test.txt' };
+      expect(tool.validateToolParams(params)).toMatch(
+        /File path must be absolute/,
+      );
+    });
+
+    it('should return error for path outside root', () => {
+      const outsidePath = path.resolve(os.tmpdir(), 'outside-root.txt');
+      const params: ReadFileToolParams = { path: outsidePath };
+      expect(tool.validateToolParams(params)).toMatch(
+        /File path must be within the root directory/,
+      );
+    });
+
+    it('should return error for negative offset', () => {
+      const params: ReadFileToolParams = {
+        path: path.join(tempRootDir, 'test.txt'),
+        offset: -1,
+        limit: 10,
+      };
+      expect(tool.validateToolParams(params)).toBe(
+        'Offset must be a non-negative number',
+      );
+    });
+
+    it('should return error for non-positive limit', () => {
+      const paramsZero: ReadFileToolParams = {
+        path: path.join(tempRootDir, 'test.txt'),
+        offset: 0,
+        limit: 0,
+      };
+      expect(tool.validateToolParams(paramsZero)).toBe(
+        'Limit must be a positive number',
+      );
+      const paramsNegative: ReadFileToolParams = {
+        path: path.join(tempRootDir, 'test.txt'),
+        offset: 0,
+        limit: -5,
+      };
+      expect(tool.validateToolParams(paramsNegative)).toBe(
+        'Limit must be a positive number',
+      );
+    });
+
+    it('should return error for schema validation failure (e.g. missing path)', () => {
+      const params = { offset: 0 } as unknown as ReadFileToolParams;
+      expect(tool.validateToolParams(params)).toBe(
+        'Parameters failed schema validation.',
+      );
+    });
+  });
+
+  describe('getDescription', () => {
+    it('should return a shortened, relative path', () => {
+      const filePath = path.join(tempRootDir, 'sub', 'dir', 'file.txt');
+      const params: ReadFileToolParams = { path: filePath };
+      // Assuming tempRootDir is something like /tmp/read-file-tool-root-XXXXXX
+      // The relative path would be sub/dir/file.txt
+      expect(tool.getDescription(params)).toBe('sub/dir/file.txt');
+    });
+
+    it('should return . if path is the root directory', () => {
+      const params: ReadFileToolParams = { path: tempRootDir };
+      expect(tool.getDescription(params)).toBe('.');
+    });
+  });
+
+  describe('execute', () => {
+    it('should return validation error if params are invalid', async () => {
+      const params: ReadFileToolParams = { path: 'relative/path.txt' };
+      const result = await tool.execute(params, abortSignal);
+      expect(result.llmContent).toMatch(/Error: Invalid parameters provided/);
+      expect(result.returnDisplay).toMatch(/File path must be absolute/);
+    });
+
+    it('should return error from processSingleFileContent if it fails', async () => {
+      const filePath = path.join(tempRootDir, 'error.txt');
+      const params: ReadFileToolParams = { path: filePath };
+      const errorMessage = 'Simulated read error';
+      mockProcessSingleFileContent.mockResolvedValue({
+        llmContent: `Error reading file ${filePath}: ${errorMessage}`,
+        returnDisplay: `Error reading file ${filePath}: ${errorMessage}`,
+        error: errorMessage,
+      });
+
+      const result = await tool.execute(params, abortSignal);
+      expect(mockProcessSingleFileContent).toHaveBeenCalledWith(
+        filePath,
+        tempRootDir,
+        undefined,
+        undefined,
+      );
+      expect(result.llmContent).toContain(errorMessage);
+      expect(result.returnDisplay).toContain(errorMessage);
+    });
+
+    it('should return success result for a text file', async () => {
+      const filePath = path.join(tempRootDir, 'textfile.txt');
+      const fileContent = 'This is a test file.';
+      const params: ReadFileToolParams = { path: filePath };
+      mockProcessSingleFileContent.mockResolvedValue({
+        llmContent: fileContent,
+        returnDisplay: `Read text file: ${path.basename(filePath)}`,
+      });
+
+      const result = await tool.execute(params, abortSignal);
+      expect(mockProcessSingleFileContent).toHaveBeenCalledWith(
+        filePath,
+        tempRootDir,
+        undefined,
+        undefined,
+      );
+      expect(result.llmContent).toBe(fileContent);
+      expect(result.returnDisplay).toBe(
+        `Read text file: ${path.basename(filePath)}`,
+      );
+    });
+
+    it('should return success result for an image file', async () => {
+      const filePath = path.join(tempRootDir, 'image.png');
+      const imageData = {
+        inlineData: { mimeType: 'image/png', data: 'base64...' },
+      };
+      const params: ReadFileToolParams = { path: filePath };
+      mockProcessSingleFileContent.mockResolvedValue({
+        llmContent: imageData,
+        returnDisplay: `Read image file: ${path.basename(filePath)}`,
+      });
+
+      const result = await tool.execute(params, abortSignal);
+      expect(mockProcessSingleFileContent).toHaveBeenCalledWith(
+        filePath,
+        tempRootDir,
+        undefined,
+        undefined,
+      );
+      expect(result.llmContent).toEqual(imageData);
+      expect(result.returnDisplay).toBe(
+        `Read image file: ${path.basename(filePath)}`,
+      );
+    });
+
+    it('should pass offset and limit to processSingleFileContent', async () => {
+      const filePath = path.join(tempRootDir, 'paginated.txt');
+      const params: ReadFileToolParams = {
+        path: filePath,
+        offset: 10,
+        limit: 5,
+      };
+      mockProcessSingleFileContent.mockResolvedValue({
+        llmContent: 'some lines',
+        returnDisplay: 'Read text file (paginated)',
+      });
+
+      await tool.execute(params, abortSignal);
+      expect(mockProcessSingleFileContent).toHaveBeenCalledWith(
+        filePath,
+        tempRootDir,
+        10,
+        5,
+      );
+    });
+  });
+});