Add methods to testing suite:
	Helper methods :
	   i) containsNull()
	   ii) addDummyData()
	 Testing methods:
	    i)   iteratorBasicTest()
	    ii)  iteratorSemanticsTest()
	    iii) removeNullTest()
	    iv)  removeAllTest()
	    v)   repeatedValuesTest()
	    vi)  addNullTest()