test: to-valid-identifier-name

packages/mdx/package.json

@@ -84,7 +84,7 @@
   "scripts": {
     "prepack": "npm run build",
     "build": "rimraf \"lib/**/*.d.ts\" \"test/**/*.d.ts\" \"*.d.ts\" && tsc && type-coverage",
-    "test-api": "uvu test \"^(compile|evaluate)\\.js$\"",
+    "test-api": "uvu test \"^(compile|evaluate|to-valid-identifier-name)\\.js$\"",
     "test-coverage": "c8 --check-coverage --100 --reporter lcov npm run test-api",
     "test": "npm run build && npm run test-coverage"
   },

packages/mdx/test/to-valid-identifier-name.js

@@ -0,0 +1,45 @@
+import {test} from 'uvu'
+import * as assert from 'uvu/assert'
+import {toValidIdentifierName} from '../lib/util/to-valid-identifier-name.js'
+
+/** @param {string} invalidChar */
+function toTestFailureMessage(invalidChar) {
+  return `Invalid characters like "${invalidChar}" should be converted to underscores "_"`
+}
+
+test('toValidIdentifierName', () => {
+  // Valid strings left untouched
+  assert.equal(toValidIdentifierName('test'), 'test')
+  assert.equal(toValidIdentifierName('camelCase'), 'camelCase')
+  // Invalid cont character -> underscore
+  assert.equal(
+    toValidIdentifierName('custom-element'),
+    'custom_element',
+    toTestFailureMessage('-')
+  )
+  assert.equal(
+    toValidIdentifierName('custom element'),
+    'custom_element',
+    toTestFailureMessage(' ')
+  )
+  // Invalid starting character -> underscore
+  assert.equal(
+    toValidIdentifierName('-badStarting'),
+    '_badStarting',
+    toTestFailureMessage('-')
+  )
+  assert.equal(
+    toValidIdentifierName('1badStarting'),
+    '_badStarting',
+    toTestFailureMessage('1')
+  )
+  assert.equal(
+    toValidIdentifierName(' badStarting'),
+    '_badStarting',
+    toTestFailureMessage(' ')
+  )
+  // Empty string -> underscore
+  assert.equal('_', toValidIdentifierName(''))
+})
+
+test.run()