build: Move build related unit test into own job

We shouldn't be asserting on built assets (dist/esm) in our unit tests.

This helps unblock #4616

.github/workflows/build.yml

@@ -411,7 +411,11 @@ jobs:
         with:
           path: ${{ env.CACHED_BUILD_PATHS }}
           key: ${{ env.BUILD_CACHE_KEY }}
-      - name: Run build tests
+      - name: Run browser build tests
         run: |
           cd packages/browser
           yarn test:package
+      - name: Run utils build tests
+        run: |
+          cd packages/utils
+          yarn test:package

packages/utils/.gitignore

@@ -1,4 +1,5 @@
 *.js.map
 *.d.ts
 *.js
+!test/package/build.js
 !.eslintrc.js

packages/utils/package.json

@@ -45,7 +45,8 @@
     "lint:prettier": "prettier --check \"{src,test}/**/*.ts\"",
     "pack": "npm pack",
     "test": "jest",
-    "test:watch": "jest --watch"
+    "test:watch": "jest --watch",
+    "test:package": "node test/package/build.js"
   },
   "volta": {
     "extends": "../../package.json"

packages/utils/test/package/build.js

@@ -0,0 +1,27 @@
+const fs = require('fs');
+const path = require('path');
+
+const testStrings = [`/// <reference types="node" />`];
+
+const paths = [path.join('./dist'), path.join('./esm')];
+
+paths.forEach(dir => {
+  if (!fs.existsSync(dir)) {
+    // eslint-disable-next-line no-console
+    console.error(`${dir} doesn't exist please build first`);
+    process.exit(1);
+  }
+  const files = fs.readdirSync(dir);
+  files.forEach(file => {
+    if (file.includes('.d.ts')) {
+      testStrings.forEach(testString => {
+        const filePath = path.join(dir, file)
+        if (fs.readFileSync(filePath, 'utf8').includes(testString)) {
+          // eslint-disable-next-line no-console
+          console.error(`${filePath} contains types`);
+          process.exit(1);
+        }
+      });
+    }
+  });
+});