lib/assert/error.js
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();
}
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();
}
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 ( ) ; }
Assertion errors, can provide a detailed error messages.

inspect() and cliMessage() added to display errors with params.
Assertion errors can provide a detailed error messages .