Bug 201017 TopN, TopPercent, BottomPercent filters will lead NPE when the values contains NULL[07]
data/org.eclipse.birt.data.tests/test/org/eclipse/birt/data/engine/aggregation/TotalTest.java
ac.onRow(new Object[]{str1[i]});
        }
        ac.finish();
        assertEquals(new Double(4.928571428571429), ac.getValue());
        
        ac.start();
        ac.finish();
        assertEquals(null, ac.getValue());
        
        ac.start();
        try
        {
            ac.getValue();
            assertTrue(false);
        }
        catch(RuntimeException e)
        {
            assertTrue(true);
        }
    }
    
    public void testTotalFirst() throws Exception
    {
        IAggregation ag = BuiltInAggregationFactory.getInstance().getAggregation("first");
        Accumulator ac = ag.newAccumulator();
        assertEquals(IBuildInAggregation.TOTAL_FIRST_FUNC, ag.getName());
        assertEquals(IAggregation.SUMMARY_AGGR, ag.getType());
        assertEquals(1, ag.getParameterDefn().length);
        assertTrue(ag.getParameterDefn()[0]);