code: function AssertionFailedError(params, template) {
    this.params = params;
    this.template = template;
    // this.message = "AssertionFailedError";
    let stack = new Error().stack;
    // this.showDiff = true;
    stack = stack ? stack.split('\n').filter(line =>
      // @todo cut assert things nicer
      line.indexOf('lib/assert') < 0).join('\n') : '';
    this.showDiff = true;
  
    this.actual = this.params.actual;
    this.expected = this.params.expected;
  
    this.inspect = () => {
      const params = this.params || {};
      const msg = params.customMessage || '';
      return msg + subs(this.template, params);
    };
  
    this.cliMessage = () => this.inspect();
  }
docs: Assertion errors, can provide a detailed error messages.
  
  inspect() and cliMessage() added to display errors with params.