How do I factor out common before() calls with mocha?

I have a lot of duplication in my mocha tests:

describe("Some test", function() {
    before(helpers.testPrepare);
    beforeEach(helpers.freshDB);

    it("should ...", function(done) {
        //...
        done();
    });

    after(helpers.teardownServer);
});

describe("Another test", function() {
    before(helpers.testPrepare);
    beforeEach(helpers.freshDB);

    it("should ...", function(done) {
        //...
        done();
    });

    after(helpers.teardownServer);
});

This could cause problems if I forget to call beforeEach and it's a pain to refactor. I'd like to define a describe that ensures I always call my setup and teardown, so I can just write:

I would like to write this as:

var describe = require('./helpers').describe;

describe("Some test", function() {
    it("should ...", function(done) {
        //...
        done();
    });
});

How can I do this, since mocha is defining describe as a global? How do I ensure everything is executed in the right order?