t = db.index_check7;
t.drop();

for (var i = 0; i < 100; i++)
    t.save({x: i});

t.ensureIndex({x: 1});
assert.eq(1, t.find({x: 27}).explain(true).executionStats.totalKeysExamined, "A");

t.ensureIndex({x: -1});
assert.eq(1, t.find({x: 27}).explain(true).executionStats.totalKeysExamined, "B");

assert.eq(40, t.find({x: {$gt: 59}}).explain(true).executionStats.totalKeysExamined, "C");