Switch testing from mocha/chai/karma/c8 to vitest.

.github/workflows/main.yaml

@@ -43,9 +43,10 @@ jobs:
         node-version: ${{ matrix.node-version }}
     - name: Run tests with Node.js ${{ matrix.node-version }}
       run: npm run test-node
-  test-karma:
+  test-browser:
     runs-on: ubuntu-latest
-    timeout-minutes: 10
+    # three browser engines plus a cold browser install
+    timeout-minutes: 20
     strategy:
       matrix:
         node-version: [24.x]
@@ -58,11 +59,19 @@ jobs:
       with:
         node-version: ${{ matrix.node-version }}
     - run: npm install
-    - name: Run karma tests
-      run: npm run test-karma
+    - name: Cache Playwright browsers
+      uses: actions/cache@v4
+      with:
+        path: ~/.cache/ms-playwright
+        key: playwright-${{ runner.os }}-${{ hashFiles('package.json') }}
+    - name: Install Playwright browsers
+      run: npx playwright install --with-deps chromium firefox webkit
+    - name: Run browser tests
+      run: npm run test-browser
   coverage:
     runs-on: ubuntu-latest
-    timeout-minutes: 10
+    # the browser project runs here too, across three engines
+    timeout-minutes: 20
     strategy:
       matrix:
         node-version: [24.x]
@@ -75,6 +84,14 @@ jobs:
       with:
         node-version: ${{ matrix.node-version }}
     - run: npm install
+    # coverage runs the browser project too, so the browsers are required
+    - name: Cache Playwright browsers
+      uses: actions/cache@v4
+      with:
+        path: ~/.cache/ms-playwright
+        key: playwright-${{ runner.os }}-${{ hashFiles('package.json') }}
+    - name: Install Playwright browsers
+      run: npx playwright install --with-deps chromium firefox webkit
     - name: Generate coverage report
       run: npm run coverage-ci
     - name: Upload coverage to Codecov

.gitignore

@@ -2,12 +2,14 @@
 *.sw[nop]
 *~
 .cache
+.vitest-attachments
 .nyc_output
 .project
 .settings
 .vscode
 TAGS
 coverage
 dist
+__screenshots__
 node_modules
 reports

CHANGELOG.md

@@ -27,6 +27,33 @@
   - Test on Node.js >=22.
   - Update `engines.node` to `>=22`.
   - Update README requirements section.
+- **BREAKING**: Add an `exports` field.
+  - Only `.`, `./agentCompatibility.js`, and `./package.json` are importable;
+    other deep imports into the package are no longer reachable.
+- Switch testing from `mocha`/`chai`/`karma`/`c8` to `vitest`.
+  - `karma` is unmaintained; `vitest` covers Node.js tests, browser tests, and
+    coverage with a single tool and config.
+  - Browser tests now run via `playwright` instead of `karma`, in Chromium,
+    Firefox, and WebKit rather than Chromium alone.
+  - `npm test` now runs both the Node.js and browser suites; use
+    `npm run test-node` or `npm run test-browser` for one of them.
+  - `npm run test-karma` is replaced by `npm run test-browser`.
+  - `npm run coverage-report` is removed; use
+    `npm run coverage -- --coverage.reporter=html`.
+  - Coverage now includes the browser suite, and reported totals shift
+    slightly because `istanbul` and `c8` count executable lines differently.
+    The `istanbul` provider is used rather than `v8` because v8 coverage is
+    gathered over CDP, which only Chromium supports.
+
+### Fixed
+- Detect a possible CORS error in Firefox and WebKit, not just Chromium. The
+  `Failed to fetch "<url>". Possible CORS error.` message was produced by
+  matching Chromium's network-error text, so other engines fell through to a
+  generic error. Firefox and WebKit wording is now recognized as well.
+- Resolve `agentCompatibility` through an `exports` `browser` condition rather
+  than only the top-level `browser` field. Bundlers that do not apply the
+  `browser` field to package-internal relative imports (such as Vite) no longer
+  pull `undici` into browser builds.
 
 ### Removed
 - **BREAKING**: Remove CJS support.

lib/httpClient.js

@@ -1,7 +1,7 @@
 /*!
  * Copyright (c) 2020-2026 Digital Bazaar, Inc.
  */
-import {convertAgent} from './agentCompatibility.js';
+import {convertAgent} from '@digitalbazaar/http-client/agentCompatibility.js';
 import ky from 'ky';
 
 export {ky};
@@ -15,6 +15,23 @@ const PROXY_METHODS = new Set([
   'get', 'post', 'put', 'patch', 'head', 'delete', 'query', 'options', 'trace'
 ]);
 
+/*
+Browsers reject a blocked or failed `fetch` with a `TypeError` whose message
+is engine-specific. A cross-origin block is deliberately indistinguishable
+from any other network failure -- the response is opaque -- which is why the
+message below says "Possible". Node.js rejects with `fetch failed`, which is
+intentionally absent here: there is no CORS in Node.js, so the hint would be
+misleading. Each entry is exercised by the browser test matrix.
+*/
+const BROWSER_NETWORK_ERRORS = new Set([
+  // Chromium
+  'Failed to fetch',
+  // Firefox
+  'NetworkError when attempting to fetch resource.',
+  // WebKit
+  'Load failed'
+]);
+
 /**
  * Returns a custom httpClient instance. Used to specify default headers and
  * other default overrides.
@@ -125,10 +142,10 @@ async function _handleError({error, url}) {
 
   // handle network errors and system errors that do not have a response
   if(!error.response) {
-    if(error.message === 'Failed to fetch' ||
-      error.cause?.message === 'Failed to fetch') {
-      // ky@2 wraps the browser's underlying `TypeError: Failed to fetch`
-      // in its own `NetworkError`, with the original error as `cause`
+    if(BROWSER_NETWORK_ERRORS.has(error.message) ||
+      BROWSER_NETWORK_ERRORS.has(error.cause?.message)) {
+      // ky@2 wraps the browser's underlying `TypeError` in its own
+      // `NetworkError`, with the original error as `cause`
       error.message = `Failed to fetch "${url}". Possible CORS error.`;
     }
     // ky's TimeoutError class

package.json

@@ -5,21 +5,28 @@
   "license": "BSD-3-Clause",
   "type": "module",
   "main": "./lib/index.js",
+  "exports": {
+    ".": "./lib/index.js",
+    "./agentCompatibility.js": {
+      "react-native": "./lib/agentCompatibility-browser.js",
+      "browser": "./lib/agentCompatibility-browser.js",
+      "default": "./lib/agentCompatibility.js"
+    },
+    "./package.json": "./package.json"
+  },
   "browser": {
-    "./lib/agentCompatibility.js": "./lib/agentCompatibility-browser.js",
-    "./tests/utils.js": "./tests/utils-browser.js"
+    "./lib/agentCompatibility.js": "./lib/agentCompatibility-browser.js"
   },
   "react-native": {
     "./lib/agentCompatibility.js": "./lib/agentCompatibility-browser.js"
   },
   "scripts": {
-    "test": "npm run test-node",
-    "test-node": "cross-env NODE_ENV=test mocha --preserve-symlinks -t 30000 -A -R ${REPORTER:-spec} --require tests/test-mocha.js tests/*.spec.js",
-    "test-karma": "karma start karma.conf.cjs",
-    "test-watch": "cross-env NODE_ENV=test mocha --watch --parallel --preserve-symlinks -t 30000 -A -R ${REPORTER:-spec} --require tests/test-mocha.js tests/*.spec.js",
-    "coverage": "cross-env NODE_ENV=test c8 npm run test-node",
-    "coverage-ci": "cross-env NODE_ENV=test c8 --reporter=lcovonly --reporter=text-summary --reporter=text npm run test-node",
-    "coverage-report": "c8 report",
+    "test": "vitest run",
+    "test-node": "vitest run --project node",
+    "test-browser": "vitest run --project browser",
+    "test-watch": "vitest",
+    "coverage": "vitest run --coverage",
+    "coverage-ci": "vitest run --coverage --coverage.reporter=lcovonly --coverage.reporter=text-summary --coverage.reporter=text",
     "lint": "eslint"
   },
   "files": [
@@ -31,22 +38,13 @@
   },
   "devDependencies": {
     "@digitalbazaar/eslint-config": "^9.0.0",
-    "c8": "^12.0.0",
-    "chai": "^4.5.0",
+    "@vitest/browser-playwright": "^4.1.10",
+    "@vitest/coverage-istanbul": "^4.1.10",
     "cors": "^2.8.6",
-    "cross-env": "^10.1.0",
-    "detect-node": "^2.1.0",
     "eslint": "^10.8.1",
     "express": "^5.2.1",
-    "karma": "^6.4.4",
-    "karma-chai": "^0.1.0",
-    "karma-chrome-launcher": "^3.2.0",
-    "karma-mocha": "^2.0.1",
-    "karma-mocha-reporter": "^2.2.5",
-    "karma-sourcemap-loader": "^0.4.0",
-    "karma-webpack": "^5.0.1",
-    "mocha": "^11.8.0",
-    "webpack": "^5.109.2"
+    "playwright": "^1.62.1",
+    "vitest": "^4.1.10"
   },
   "repository": {
     "type": "git",
@@ -68,12 +66,5 @@
   "homepage": "https://github.com/digitalbazaar/http-client",
   "engines": {
     "node": ">=22"
-  },
-  "c8": {
-    "reporter": [
-      "lcov",
-      "text-summary",
-      "text"
-    ]
   }
 }