function pretest( name, options, benchmark, clbk ) {
	var fail;
	var opts;
	var tic;
	var toc;
	var b;

	// Counters to determine the number of `tic` and `toc` events:
	tic = 0;
	toc = 0;

	// Local copy:
	opts = copy( options );
	opts.iterations = 1;

	// Pretest to check for minimum requirements and/or errors...
	b = new Benchmark( name, opts, benchmark );
	b.on( 'result', onResult );
	b.on( 'tic', onTic );
	b.on( 'toc', onToc );
	b.once( 'end', onEnd );
	b.run();

	/**
	* Callback invoked upon a `result` event.
	*
	* @private
	* @param {(string|Object)} result - result
	*/
	function onResult( result ) {
		if (
			!isString( result ) &&
			!result.ok &&
			!result.todo
		) {
			fail = true;
		}
	}

	/**
	* Callback invoked upon a `tic` event.
	*
	* @private
	*/
	function onTic() {
		tic += 1;
	}

	/**
	* Callback invoked upon a `toc` event.
	*
	* @private
	*/
	function onToc() {
		toc += 1;
	}

	/**
	* Callback invoked upon an `end` event.
	*
	* @private
	* @returns {void}
	*/
	function onEnd() {
		var err;
		if ( fail ) {
			// Possibility that failure is intermittent, but we will assume that the usual case is that the failure would persist across all repeats and no sense failing multiple times when once suffices.
			err = new Error( 'unexpected error. Benchmark failed.' );
		} else if ( tic !== 1 || toc !== 1 ) {
			// Unable to do anything definitive with timing information (e.g., a tic with no toc or vice versa, or benchmark function calls neither tic nor toc).
			err = new Error( 'unexpected error. Invalid benchmark.' );
		}
		if ( err ) {
			return clbk( err );
		}
		return clbk();
	}
}
Runs pretests to sanity check and/or catch failures.

@private
@param {string} name - benchmark name
@param {Options} options - benchmark options
@param {(Function|undefined)} benchmark - function containing benchmark code
@param {Callback} clbk - callback to invoke after completing pretests