### Question:
FactPartitionBasedQueryCost implements QueryCost<FactPartitionBasedQueryCost>, Serializable { @Override public FactPartitionBasedQueryCost add(final FactPartitionBasedQueryCost other) { return new FactPartitionBasedQueryCost(partitionCost + other.partitionCost); } FactPartitionBasedQueryCost(final double partitionCost); @Override FactPartitionBasedQueryCost add(final FactPartitionBasedQueryCost other); @Override long getEstimatedExecTimeMillis(); @Override double getEstimatedResourceUsage(); @Override int compareTo(final FactPartitionBasedQueryCost o); @Override String toString();  }### Answer:
@Test public void testAdd() throws Exception { assertEquals(cost1.add(cost2), new FactPartitionBasedQueryCost(0.5)); }