mongodb/jstests/sharding/drop_configdb.js

// Test that dropping the config database is completely disabled via
// mongos and via mongod, if started with --configsvr
(function() {
"use strict";

var getConfigsvrToWriteTo = function(st) {
    if (st.configRS) {
        return st.configRS.getPrimary();
    } else {
        return st._configServers[0];
    }
};

var st = new ShardingTest({shards: 2});
var mongos = st.s;
var config = getConfigsvrToWriteTo(st).getDB('config');

// Try to drop config db via configsvr

print("1: Try to drop config database via configsvr");
assert.eq(0, config.dropDatabase().ok);
assert.eq("Cannot drop 'config' database if mongod started with --configsvr",
          config.dropDatabase().errmsg);

// Try to drop config db via mongos
var config = mongos.getDB("config");

print("1: Try to drop config database via mongos");
assert.eq(0, config.dropDatabase().ok);

// 20 = ErrorCodes::IllegalOperation
assert.eq(20, config.dropDatabase().code);

st.stop();
}());