old_contents: // Generators - Yield Statements
  // To do: make all tests pass, leave the assert lines unchanged!
  
  describe('generator instance', () => {
    
    function* generator() {
      yield 'hello';
      yield 'world';
    }
    
    // create instance
    let genInstance = generator();
    
    it('should have an undefined value property after initialisation', () => {
      let value = genInstance;
      assert.equal(value, undefined);
    });
    
    it('should have value of "hello" after first next() call', () => {
      let thisStep = genInstance.next;
      let [value, done] = [thisStep.value, thisStep.done];
      assert.equal(value, 'hello');
      assert.equal(done, false);
    });
    
    it('should have value of "world" after second next() call', () => {
      let thisStep = genInstance;
      let [value, done] = [thisStep.value, thisStep.done];  
      assert.equal(value, 'world');
      assert.equal(done, false);
    });
    
    it('done property = true after stepping past all yield statements', () => {
      let done = genInstance.done;
      assert.equal(done, true);
    });
  
  });
new_contents: // Generators - Yield Statements
  // To do: make all tests pass, leave the assert lines unchanged!
  
  describe('generator instance', () => {
    
    function* generator() {
      yield 'hello';
      yield 'world';
    }
    
    // create instance
    let genInstance = generator();
    
    it('should have an undefined value property after initialisation', () => {
      let value = genInstance;
      assert.equal(value, undefined);
    });
    
    it('should have value of "hello" after first next() call', () => {
      let thisStep = genInstance.next;
      let [value, done] = [thisStep.value, thisStep.done];
      assert.equal(value, 'hello');
      assert.equal(done, false);
    });
    
    it('should have value of "world" after second next() call', () => {
      let thisStep = genInstance;
      let [value, done] = [thisStep.value, thisStep.done];  
      assert.equal(value, 'world');
      assert.equal(done, false);
    });
    
    it('done property = true after stepping past all yield statements', () => {
      let done = genInstance.done;
      assert.equal(done, true);
    });
  
  });
  
subject: add closing newline