function onTest( error, time ) {
		if ( error ) {
			return done( error );
		}
		if ( !isArray( time ) || time.length !== 2 ) {
			// This should only happen if someone is a bad actor and attempts to call the `done` callback without providing timing results.
			error = new Error( 'evaluation error. Did not receive timing results.' );
			return done( error );
		}
		if ( opts.iterations === null ) {
			opts.iterations = ITERATIONS;
			return next( onRun );
		}
		// Begin timing the snippet...
		return next( onFinish );
	}
Callback invoked after completing pretest.

@private
@param {(Error|null)} error - error object
@param {NonNegativeIntegerArray} time - results
@returns {void}