Try to clarify repl13 test.

1 files changed, 22 insertions, 4 deletions

diff --git a/jstests/repl/repl13.js b/jstests/repl/repl13.js
index 403effeb846..460e5a8fdde 100644
--- a/jstests/repl/repl13.js
+++ b/jstests/repl/repl13.js
@@ -1,10 +1,17 @@
 // Test update modifier uassert during initial sync. SERVER-4781
 
+function debug( x ) {
+    if ( 0 ) {
+        printjson( x );
+    }
+}
+
 rt = new ReplTest( "repl13tests" );
 
 m = rt.start( true );
 mc = m.getDB( 'd' )[ 'c' ];
 
+// Insert some documents with a:{} fields.
 for( i = 0; i < 100000; ++i ) {
     mc.save( {_id:i,a:{}} );
 }
@@ -13,16 +20,27 @@ m.getDB( 'd' ).getLastError();
 s = rt.start( false );
 sc = s.getDB( 'd' )[ 'c' ];
 
-assert.soon( function() { printjson( sc.count() ); return sc.count() > 0; } );
+// Wait for the initial clone to begin.
+assert.soon( function() { debug( sc.count() ); return sc.count() > 0; } );
 
+// Update documents that will be cloned last with the intent that an updated version will be cloned.
+// This may cause an assertion when an update that was successfully applied to the original version
+// of a document is replayed against an updated version of the same document.
 for( i = 99999; i >= 90000; --i ) {
     // If the document is cloned as {a:1}, the {$set:{'a.b':1}} modifier will uassert.
     mc.update( {_id:i}, {$set:{'a.b':1}} );
     mc.update( {_id:i}, {$set:{a:1}} );    
 }
 
-mc.save( {} )
+// The initial sync completes and subsequent writes succeed, in spite of any assertions that occur
+// when the update operations above are replicated.
+mc.save( {} );
 assert.soon( function() { return sc.count() == 100001; } );
+mc.save( {} );
+assert.soon( function() { return sc.count() == 100002; } );
+
+debug( sc.findOne( {_id:99999} ) );
+debug( sc.findOne( {_id:90000} ) );
 
-printjson( sc.findOne( {_id:99999} ) );
-printjson( sc.findOne( {_id:90000} ) );
+assert.eq( 1, sc.findOne( {_id:99999} ).a );
+assert.eq( 1, sc.findOne( {_id:90000} ).a );