getComputedStyle.getPropertyValue returns empty strings in unit test

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1

Hi,
I have a method in component -

  /**
   * Calculate if horizontal stepper would fit within screen
   */
  private canShowHorizontalStepper(): boolean {
    const elementStyles = getComputedStyle(this.el);
    const stepWidth = elementStyles
      .getPropertyValue('--step-width-md')
      .replace(/\D/g, '');
    const lineWidth = elementStyles
      .getPropertyValue('--step-horizontal-line-width')
      .replace(/\D/g, '');

    return window.innerWidth < (
      (+stepWidth * this.stepperData.length) + (+lineWidth * this.stepperData.length - 1)
    );
  }

Which works correctly in storybook, but when running unit test both css properties are returned as empty strings;

ps. these css properties are defined inside component style :host {}