@Override
    public String toString() {
        return "Trade{" + "type=" + type + ", index=" + index + ", price=" + pricePerAsset + ", amount=" + amount + '}';
    }
@Test
    public void overrideToString() {
        assertEquals(opEquals1.toString(), opEquals2.toString());

        assertNotEquals(opEquals1.toString(), opNotEquals1.toString());
        assertNotEquals(opEquals1.toString(), opNotEquals2.toString());
    }