old_contents: it('has correct instance', function () {
  	expect(Number.isNaN).to.be.a(Function);
  });
  
  it('has correct argument length', function () {
  	expect(Number.isNaN.length).to.be(1);
  });
  
  it('returns true with NaN values', function () {
  	expect(Number.isNaN(NaN)).to.be(true);
  	expect(Number.isNaN(Number.NaN)).to.be(true);
  	expect(Number.isNaN(0/0)).to.be(true);
  });
  
  it('retuns false for valid numbers and non-number data types', function () {
  		expect(Number.isNaN("NaN")).to.be(false);
  		expect(Number.isNaN(undefined)).to.be(false);
  		expect(Number.isNaN({})).to.be(false);
  		expect(Number.isNaN("blabla")).to.be(false);
  		expect(Number.isNaN(true)).to.be(false);
  		expect(Number.isNaN(37)).to.be(false);
  		expect(Number.isNaN("37")).to.be(false);
  });	
new_contents: it('has correct instance', function () {
  	expect(Number.isNaN).to.be.a(Function);
  });
  
  it('has correct argument length', function () {
  	expect(Number.isNaN.length).to.be(1);
  });
  
  it('returns true with NaN values', function () {
  	expect(Number.isNaN(NaN)).to.be(true);
  	expect(Number.isNaN(Number.NaN)).to.be(true);
  	expect(Number.isNaN(0/0)).to.be(true);
  });
  
  it('retuns false for valid numbers and non-number data types', function () {
  	expect(Number.isNaN("NaN")).to.be(false);
  	expect(Number.isNaN(undefined)).to.be(false);
  	expect(Number.isNaN({})).to.be(false);
  	expect(Number.isNaN("blabla")).to.be(false);
  	expect(Number.isNaN(true)).to.be(false);
  	expect(Number.isNaN(37)).to.be(false);
  	expect(Number.isNaN("37")).to.be(false);
  });
  
subject: Fix wonky indent