### Question:
Subscription { public DataExpr dataExpr() { return expr; } Subscription(); DataExpr dataExpr(); String getId(); void setId(String id); Subscription withId(String id); String getExpression(); void setExpression(String expression); Subscription withExpression(String expression); long getFrequency(); void setFrequency(long frequency); Subscription withFrequency(long frequency); @Override boolean equals(Object o); @Override int hashCode(); @Override String toString();  }### Answer:
@Test public void dataExpr() { Subscription sub = new Subscription().withExpression(":true,:sum"); Assertions.assertEquals(new DataExpr.Sum(Query.TRUE), sub.dataExpr()); }