diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dd8914c..73e6822 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,27 +21,28 @@ jobs:
         node-version-file: .tool-versions
         cache: npm
 
-    - name: Install dependencies
-      run: npm i
+    - name: Clean install dependencies
+      run: npm ci
 
     - name: Lint
       run: yarn lint
 
   test:
-    runs-on: ubuntu-22.04
-    timeout-minutes: 10
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        node-version: [16.x, 18.x, 20.x]
+    runs-on: ${{ matrix.os }}
     steps:
-    - name: Checkout code
-      uses: actions/checkout@v4
-
-    - name: Setup node
+    - uses: actions/checkout@v4
+    - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v4
       with:
-        node-version-file: .tool-versions
-        cache: npm
+        node-version: ${{ matrix.node-version }}
 
-    - name: Install dependencies
-      run: npm i
+    - name: Clean install dependencies
+      run: npm ci
 
-    - name: Test
-      run: npm test
+    - run: npm run test-coverage -- --reporter=verbose
+      env:
+        CI_OS: ${{ runner.os }}
diff --git a/src/core/packager.ts b/src/core/packager.ts
index 4387fbe..943fa9e 100644
--- a/src/core/packager.ts
+++ b/src/core/packager.ts
@@ -5,6 +5,7 @@ import { processFile as defaultProcessFile } from '../utils/fileHandler.js';
 import {
   getGitignorePatterns as defaultGetGitignorePatterns,
   createIgnoreFilter as defaultCreateIgnoreFilter,
+  IgnoreFilter,
 } from '../utils/gitignoreUtils.js';
 import { generateOutput as defaultGenerateOutput } from './outputGenerator.js';
 import { defaultIgnoreList } from '../utils/defaultIgnore.js';
@@ -64,7 +65,7 @@ async function packDirectory(
   dir: string,
   relativePath: string,
   config: RepopackConfigMerged,
-  ignoreFilter: (path: string) => boolean,
+  ignoreFilter: IgnoreFilter,
   deps: Dependencies,
 ): Promise<{ path: string; content: string }[]> {
   const entries = await fs.readdir(dir, { withFileTypes: true });
diff --git a/src/utils/gitignoreUtils.ts b/src/utils/gitignoreUtils.ts
index 9fe65cc..246d04f 100644
--- a/src/utils/gitignoreUtils.ts
+++ b/src/utils/gitignoreUtils.ts
@@ -20,7 +20,9 @@ export function parseGitignoreContent(content: string): string[] {
     .filter((line) => line && !line.startsWith('#'));
 }
 
-export function createIgnoreFilter(patterns: string[]): (path: string) => boolean {
+export type IgnoreFilter = (path: string) => boolean;
+
+export function createIgnoreFilter(patterns: string[]): IgnoreFilter {
   const ig = ignore.default().add(patterns);
   return (filePath: string) => !ig.ignores(filePath);
 }
diff --git a/tests/utils/gitignoreUtils.test.ts b/tests/utils/gitignoreUtils.test.ts
index 48b7591..78c6230 100644
--- a/tests/utils/gitignoreUtils.test.ts
+++ b/tests/utils/gitignoreUtils.test.ts
@@ -2,58 +2,178 @@ import { expect, test, vi, describe, beforeEach } from 'vitest';
 import { getGitignorePatterns, parseGitignoreContent, createIgnoreFilter } from '../../src/utils/gitignoreUtils.js';
 import path from 'path';
 import * as fs from 'fs/promises';
+import os from 'os';
 
 vi.mock('fs/promises');
 
+const isWindows = os.platform() === 'win32';
+
 describe('gitignoreUtils', () => {
   beforeEach(() => {
     vi.resetAllMocks();
   });
 
-  test('getGitignorePatterns should read and parse .gitignore file', async () => {
-    const mockContent = `
+  describe('getGitignorePatterns', () => {
+    test('should read and parse .gitignore file', async () => {
+      const mockContent = `
 # Comment
 node_modules
 *.log
 .DS_Store
-    `;
-    vi.mocked(fs.readFile).mockResolvedValue(mockContent);
+      `;
+      vi.mocked(fs.readFile).mockResolvedValue(mockContent);
 
-    const patterns = await getGitignorePatterns('/mock/root');
+      const patterns = await getGitignorePatterns('/mock/root');
 
-    expect(fs.readFile).toHaveBeenCalledWith(path.join('/mock/root', '.gitignore'), 'utf-8');
-    expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
-  });
+      expect(fs.readFile).toHaveBeenCalledWith(path.join('/mock/root', '.gitignore'), 'utf-8');
+      expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
+    });
+
+    test('should return empty array if .gitignore is not found', async () => {
+      vi.mocked(fs.readFile).mockRejectedValue(new Error('File not found'));
+
+      const patterns = await getGitignorePatterns('/mock/root');
 
-  test('getGitignorePatterns should return empty array if .gitignore is not found', async () => {
-    vi.mocked(fs.readFile).mockRejectedValue(new Error('File not found'));
+      expect(patterns).toEqual([]);
+    });
 
-    const patterns = await getGitignorePatterns('/mock/root');
+    test('should handle CRLF line endings', async () => {
+      const mockContent = 'node_modules\r\n*.log\r\n.DS_Store';
+      vi.mocked(fs.readFile).mockResolvedValue(mockContent);
 
-    expect(patterns).toEqual([]);
+      const patterns = await getGitignorePatterns('/mock/root');
+
+      expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
+    });
   });
 
-  test('parseGitignoreContent should correctly parse gitignore content', () => {
-    const content = `
+  describe('parseGitignoreContent', () => {
+    test('should correctly parse gitignore content', () => {
+      const content = `
 # Comment
 node_modules
 *.log
 
 .DS_Store
-    `;
+      `;
+
+      const patterns = parseGitignoreContent(content);
+
+      expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
+    });
+
+    test('should handle mixed line endings', () => {
+      const content = 'node_modules\n*.log\r\n.DS_Store\r';
 
-    const patterns = parseGitignoreContent(content);
+      const patterns = parseGitignoreContent(content);
 
-    expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
+      expect(patterns).toEqual(['node_modules', '*.log', '.DS_Store']);
+    });
   });
 
-  test('createIgnoreFilter should create a function that correctly filters paths', () => {
-    const patterns = ['node_modules', '*.log', '.DS_Store'];
-    const filter = createIgnoreFilter(patterns);
+  describe('createIgnoreFilter', () => {
+    test('should create a function that correctly filters paths', () => {
+      const patterns = ['node_modules', '*.log', '.DS_Store'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('src/index.js')).toBe(true);
+      expect(filter('node_modules/package/index.js')).toBe(false);
+      expect(filter('logs/error.log')).toBe(false);
+      expect(filter('.DS_Store')).toBe(false);
+    });
+
+    test('should correctly ignore files with different path separators', () => {
+      const patterns = ['*.md', '*.svg', '*.css', 'node_modules/**'];
+      const filter = createIgnoreFilter(patterns);
+
+      // UNIX-style paths
+      expect(filter('README.md')).toBe(false);
+      expect(filter('src/assets/logo.svg')).toBe(false);
+      expect(filter('styles/main.css')).toBe(false);
+      expect(filter('node_modules/package/index.js')).toBe(false);
+
+      // Files that should not be ignored
+      expect(filter('src/index.js')).toBe(true);
+    });
+
+    test.runIf(isWindows)('should correctly ignore files with Windows-style paths', () => {
+      const patterns = ['*.md', '*.svg', '*.css', 'node_modules/**'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('docs\\README.md')).toBe(false);
+      expect(filter('src\\assets\\logo.svg')).toBe(false);
+      expect(filter('styles\\main.css')).toBe(false);
+      expect(filter('node_modules\\package\\index.js')).toBe(false);
+      expect(filter('src\\components\\Button.js')).toBe(true);
+    });
+
+    test('should handle nested directory patterns correctly', () => {
+      const patterns = ['test/**/*.spec.js', 'build/**'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('test/unit/component.spec.js')).toBe(false);
+      expect(filter('build/output.js')).toBe(false);
+
+      expect(filter('src/test/helper.js')).toBe(true);
+    });
+
+    test.runIf(isWindows)('should handle nested directory patterns with Windows-style paths', () => {
+      const patterns = ['test/**/*.spec.js', 'build/**'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('src\\build\\utils.js')).toBe(true);
+      expect(filter('test\\integration\\api.spec.js')).toBe(false);
+      expect(filter('build\\temp\\cache.json')).toBe(false);
+    });
+
+    test('should correctly handle patterns with special characters', () => {
+      const patterns = ['**/*.min.js', '**/#temp#', '**/node_modules'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('dist/bundle.min.js')).toBe(false);
+      expect(filter('temp/#temp#/file.txt')).toBe(false);
+      expect(filter('project/node_modules/package/index.js')).toBe(false);
+
+      expect(filter('src/app.js')).toBe(true);
+      expect(filter('docs/temp/file.txt')).toBe(true);
+    });
+
+    test('should handle case sensitivity correctly', () => {
+      const patterns = ['*.MD', 'TEST'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('readme.md')).toBe(false);
+      expect(filter('test/file.txt')).toBe(false);
+
+      expect(filter('README.MD')).toBe(false);
+      expect(filter('TEST/file.txt')).toBe(false);
+    });
+
+    test('should handle symlinks correctly', () => {
+      const patterns = ['symlink', 'real_dir'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter('symlink')).toBe(false);
+      expect(filter('real_dir')).toBe(false);
+      expect(filter('symlink/file.txt')).toBe(false);
+      expect(filter('real_dir/file.txt')).toBe(false);
+    });
+
+    test('should handle long paths correctly', () => {
+      const longPath = 'a'.repeat(200) + '/file.txt';
+      const patterns = ['**/*.txt'];
+      const filter = createIgnoreFilter(patterns);
+
+      expect(filter(longPath)).toBe(false);
+    });
+
+    test('should handle Unicode characters in paths and patterns', () => {
+      const patterns = ['📁/*', '*.🚀'];
+      const filter = createIgnoreFilter(patterns);
 
-    expect(filter('src/index.js')).toBe(true);
-    expect(filter('node_modules/package/index.js')).toBe(false);
-    expect(filter('logs/error.log')).toBe(false);
-    expect(filter('.DS_Store')).toBe(false);
+      expect(filter('📁/file.txt')).toBe(false);
+      expect(filter('document.🚀')).toBe(false);
+      expect(filter('normal/path/file.txt')).toBe(true);
+    });
   });
 });
diff --git a/vite.config.mts b/vite.config.mts
index e75dd23..13ab703 100644
--- a/vite.config.mts
+++ b/vite.config.mts
@@ -6,6 +6,7 @@ export default defineConfig({
     environment: 'node',
     include: ['tests/**/*.test.ts'],
     coverage: {
+      include: ['src/**/*'],
       reporter: ['text', 'json', 'html'],
     },
   }