Use coverage-node for code coverage.

changelog.md

@@ -11,7 +11,7 @@
 - Added a package [`exports`](https://nodejs.org/api/packages.html#packages_exports) field with [conditional exports](https://nodejs.org/api/packages.html#packages_conditional_exports) to support native ESM in Node.js and keep internal code private, whilst avoiding the [dual package hazard](https://nodejs.org/api/packages.html#packages_dual_package_hazard). Published files have been reorganized, so previously undocumented deep imports will need to be rewritten according to the newly documented paths.
 - Removed Babel related dev dependencies, config, and scripts. Published modules now contain more modern ES syntax.
 - Published modules now contain JSDoc comments, which might affect TypeScript projects.
-- Added a package `test:api` script to test the API, using [`test-director`](https://npm.im/test-director) and ESM in `.mjs` files.
+- Added a package `test:api` script to test the API, using [`coverage-node`](https://npm.im/coverage-node), [`test-director`](https://npm.im/test-director), and ESM in `.mjs` files.
 
 ### Patch
 

package.json

@@ -40,6 +40,7 @@
   },
   "browserslist": "Node 12.20 - 13 and Node < 13, Node >= 14.13, > 0.5%, not OperaMini all, not IE > 0, not dead",
   "devDependencies": {
+    "coverage-node": "^5.0.1",
     "esbuild": "^0.12.1",
     "eslint": "^7.27.0",
     "eslint-config-env": "^20.0.1",
@@ -60,7 +61,7 @@
     "test:eslint": "eslint --ext mjs,js .",
     "test:prettier": "prettier -c .",
     "test:jsdoc": "jsdoc-md -c",
-    "test:api": "node test/index.mjs",
+    "test:api": "coverage-node test/index.mjs",
     "prepublishOnly": "npm test"
   }
 }