@Test
public void testSubtractVectorWithoutCopy() {

	double[] value1 = { 1, 2 };
	double[] value2 = { 2, 3 };
	double[] sum = { 3, 5 };
	IVector toSubtract = new SparseDoubleVector(value1);
	IVector vector = new SparseDoubleVector(sum);
	vector.subtractVector(toSubtract);
	assertEquals(vector, new SparseDoubleVector(value2));
}