wct-mocha.js:2384 Error stamping
<template>โ#document-fragment<counter-element>โ</counter-element>โ</template>โ
TypeError: window.ShadyCSS.ScopingShim.prepareAdoptedCssText is not a function
at HTMLElement.adoptStyles (lit-element.ts:140)
at HTMLElement.initialize (lit-element.ts:95)
at new UpdatingElement (updating-element.ts:253)
at new LitElement (lit-element.ts:25)
at new MixinClass (i18n.js:48)
at new I18nBaseElement (i18n.js:100)
at new CounterElement (counter-element.js:67)
at ye (CustomElementInternals.js:266)
at Q.e (CustomElementInternals.js:177)
at Q (CustomElementInternals.js:231)