Refactor test helpers and add auth header forwarding tests

Modularizes test helpers into separate files for assertions, generators, and mocks, and updates imports for platform tests. Adds new tests to verify Authorization header forwarding for authenticated requests. Cleans up and simplifies test setup, and updates fixtures for clarity and maintainability.

test/helpers/mocks.js

@@ -0,0 +1,124 @@
+/**
+ * Mock creation utilities for tests
+ */
+
+/**
+ * Create a mock request with default options
+ * @param {string} url - Request URL
+ * @param {Object} options - Request options
+ * @returns {Request} Mock request object
+ */
+export function createMockRequest(url, options = {}) {
+  const defaultOptions = {
+    method: 'GET',
+    headers: {
+      'User-Agent': 'Mozilla/5.0 (Test)',
+      Accept: '*/*'
+    }
+  };
+
+  return new Request(url, { ...defaultOptions, ...options });
+}
+
+/**
+ * Create a mock response with default options
+ * @param {string} body - Response body
+ * @param {Object} options - Response options
+ * @returns {Response} Mock response object
+ */
+export function createMockResponse(body = 'OK', options = {}) {
+  const defaultOptions = {
+    status: 200,
+    statusText: 'OK',
+    headers: {
+      'Content-Type': 'text/plain'
+    }
+  };
+
+  return new Response(body, { ...defaultOptions, ...options });
+}
+
+/**
+ * Create a Git request for testing
+ * @param {string} url - Git repository URL
+ * @param {string} service - Git service (upload-pack or receive-pack)
+ * @returns {Request} Git request object
+ */
+export function createGitRequest(url, service = 'git-upload-pack') {
+  const gitUrl = url.includes('?') ? `${url}&service=${service}` : `${url}?service=${service}`;
+
+  return new Request(gitUrl, {
+    method: service === 'git-upload-pack' ? 'GET' : 'POST',
+    headers: {
+      'User-Agent': 'git/2.34.1',
+      'Git-Protocol': 'version=2',
+      ...(service !== 'git-upload-pack' && {
+        'Content-Type': `application/x-${service}-request`
+      })
+    }
+  });
+}
+
+/**
+ * Create a Docker request for testing
+ * @param {string} url - Docker registry URL
+ * @param {Object} options - Request options
+ * @returns {Request} Docker request object
+ */
+export function createDockerRequest(url, options = {}) {
+  return new Request(url, {
+    method: 'GET',
+    headers: {
+      'User-Agent': 'docker/24.0.0',
+      Accept: 'application/vnd.docker.distribution.manifest.v2+json',
+      ...options.headers
+    },
+    ...options
+  });
+}
+
+/**
+ * Mock fetch function for testing
+ * @param {string} url - Request URL
+ * @param {Object} options - Fetch options
+ * @returns {Promise<Response>} Mock response
+ */
+export function mockFetch(url, options = {}) {
+  return new Promise(resolve => {
+    setTimeout(() => {
+      if (url.includes('error')) {
+        resolve(createMockResponse('Server Error', { status: 500 }));
+      } else if (url.includes('notfound')) {
+        resolve(createMockResponse('Not Found', { status: 404 }));
+      } else {
+        resolve(createMockResponse('Mock Response', { status: 200 }));
+      }
+    }, 10);
+  });
+}
+
+/**
+ * Create a mock npm registry response
+ * @param {string} packageName - Package name
+ * @param {string} version - Package version
+ * @returns {Object} Mock npm registry response
+ */
+export function createMockNpmRegistryResponse(packageName, version = '1.0.0') {
+  return {
+    name: packageName,
+    versions: {
+      [version]: {
+        name: packageName,
+        version,
+        dist: {
+          tarball: `https://registry.npmjs.org/${packageName}/-/${packageName}-${version}.tgz`,
+          shasum: 'mock-shasum',
+          integrity: 'mock-integrity'
+        }
+      }
+    },
+    'dist-tags': {
+      latest: version
+    }
+  };
+}