1 files changed, 34 insertions, 0 deletions
diff --git a/jstests/core/reversecursor.js b/jstests/core/reversecursor.js
new file mode 100644
index 00000000000..bb661952fc9
--- /dev/null
+++ b/jstests/core/reversecursor.js
@@ -0,0 +1,34 @@
+// Test to make sure that a reverse cursor can correctly handle empty extents (SERVER-6980)
+
+// Create a collection with three small extents
+db.jstests_reversecursor.drop();
+db.runCommand({"create":"jstests_reversecursor", $nExtents: [4096,4096,4096]});
+
+// Function to check whether all three extents are non empty
+function extentsSpanned() {
+    var extents = db.jstests_reversecursor.validate(true).extents;
+    return (extents[0].firstRecord != "null" &&
+            extents[1].firstRecord != "null" &&
+            extents[2].firstRecord != "null");
+}
+
+// Insert enough documents to span all three extents
+a = 0;
+while (!extentsSpanned()) {
+    db.jstests_reversecursor.insert({a:a++});
+}
+
+// Delete all the elements in the middle
+db.jstests_reversecursor.remove({a:{$gt:0,$lt:a-1}});
+
+// Make sure the middle extent is empty and that both end extents are not empty
+assert.eq(db.jstests_reversecursor.validate(true).extents[1].firstRecord, "null");
+assert.eq(db.jstests_reversecursor.validate(true).extents[1].lastRecord, "null");
+assert.neq(db.jstests_reversecursor.validate(true).extents[0].firstRecord, "null");
+assert.neq(db.jstests_reversecursor.validate(true).extents[0].lastRecord, "null");
+assert.neq(db.jstests_reversecursor.validate(true).extents[2].firstRecord, "null");
+assert.neq(db.jstests_reversecursor.validate(true).extents[2].lastRecord, "null");
+
+// Make sure that we get the same number of elements for both the forward and reverse cursors
+assert.eq(db.jstests_reversecursor.find().sort({$natural:1}).toArray().length, 2);
+assert.eq(db.jstests_reversecursor.find().sort({$natural:-1}).toArray().length, 2);