text: var nthCheck = require("../lib/nth-check.js"),
      assert = require("assert");
  
  var invalid = ["-", "asdf", "2n+-0", "2+0", "- 1n", "-1 n"];
  function parseInvalid(){
  	invalid.forEach(function(formula){
  		assert.throws(function(){
  				nthCheck.parse(formula);
  			},
  			SyntaxError,
  			formula
  		);
  	});
  }
  
  var valid = {
  	"1": [ 0, 1 ],
  	"2": [ 0, 2 ],
  	"3": [ 0, 3 ],
  	"5": [ 0, 5 ],
  	" 1 ": [ 0, 1 ],
  	" 5 ": [ 0, 5 ],
  	"+2n + 1": [ 2, 1 ],
  	"-1": [ 0, -1 ],
  	"-1n + 3": [ -1, 3 ],
  	"-1n+3": [ -1, 3 ],
  	"-n+2": [ -1, 2 ],
  	"-n+3": [ -1, 3 ],
  	"0n+3": [ 1, 3 ],
  	"1n": [ 1, 0 ],
  	"1n+0": [ 1, 0 ],
  	"2n": [ 2, 0 ],
  	"2n + 1": [ 2, 1 ],
  	"2n+1": [ 2, 1 ],
  	"3n": [ 3, 0 ],
  	"3n+0": [ 3, 0 ],
  	"3n+1": [ 3, 1 ],
  	"3n+2": [ 3, 2 ],
  	"3n+3": [ 3, 3 ],
  	"3n-1": [ 3, -1 ],
  	"3n-2": [ 3, -2 ],
  	"3n-3": [ 3, -3 ],
  	even: [ 2, 0 ],
  	n: [ 1, 0 ],
  	"n+2": [ 1, 2 ],
  	odd: [ 2, 1 ],
  
  	//surprisingly, neither sizzle, qwery or nwmatcher cover these cases
  	"-4n+13": [-4, 13],
  	"-2n + 12": [-2, 12]
  };
  
  function parseValid(){
  	Object.keys(valid).forEach(function(formula){
  		assert.deepEqual(nthCheck.parse(formula), valid[formula], formula);
  	});
  }
  
  function testValid(){
  	Object.keys(valid).forEach(function(formula){
  		testFormula(valid[formula], formula);
  	});
  }
  
  var LIMIT = 1e3;
  
  var valArray = (function(){
  	var elems = [];
  	for(var i = 0; i <= LIMIT; i++) elems.push(i);
  	return elems;
  }());
  
  function testFormula(formula, name){
  	var filtered = valArray.filter(nthCheck.compile(formula)),
  	    iterated = stupidNth(formula);
  
  	try {
  		assert.deepEqual(filtered, iterated, name);
  	} catch(e){
  		e.expected = JSON.stringify(iterated) + " " + name;
  		e.actual = JSON.stringify(filtered) + " " + name;
  		throw e;
  	}
  }
  
  function stupidNth(formula, limit){
  	var a = formula[0],
  	    b = formula[1];
  
  	if(a === 0 && b > 0) return [b - 1];
  
  	/*
  	var result = [];
  
  	for(var i = b; a > 0 ? i <= limit : i >= 1; i += a){
  		if(i > 0) result.push(i - 1);
  	}
  
  	return result.sort();
  	*/
  
  	//taken from qwery
  	return valArray.filter(function(val){
  		for(var i = b, l = valArray.length; ((a > 0) ? (i <= l) : (i >= 1)); i += a){
  			if(val === valArray[i - 1]) return true;
  		}
  	});
  }
  
  describe("nth-checks", function(){
  	describe("parser", function(){
  		it("parse invalid", parseInvalid);
  		it("parse valid", parseValid);
  	});
  
  	it("check values", testValid);
  });