t = db.jstests_group6; t.drop(); for( i = 1; i <= 10; ++i ) { t.save( {i:new NumberLong( i ),y:1} ); } assert.eq.automsg( "55", "t.group( {key:'y', reduce:function(doc,out){ out.i += doc.i; }, initial:{i:0} } )[ 0 ].i" ); t.drop(); for( i = 1; i <= 10; ++i ) { if ( i % 2 == 0 ) { t.save( {i:new NumberLong( i ),y:1} ); } else { t.save( {i:i,y:1} ); } } assert.eq.automsg( "55", "t.group( {key:'y', reduce:function(doc,out){ out.i += doc.i; }, initial:{i:0} } )[ 0 ].i" ); t.drop(); for( i = 1; i <= 10; ++i ) { if ( i % 2 == 1 ) { t.save( {i:new NumberLong( i ),y:1} ); } else { t.save( {i:i,y:1} ); } } assert.eq.automsg( "55", "t.group( {key:'y', reduce:function(doc,out){ out.i += doc.i; }, initial:{i:0} } )[ 0 ].i" );