When a module is 'require'd before mockery is enabled, mockery will still provide the mock when enabled, bypassing the cache entry.

test_cache_bypass.js

var mockery = require('../mockery'),
    fake_module;

var mock_fake_module = {
    foo: function () {
        return 'mocked foo';
    }
};

fake_module = require('./fixtures/fake_module');
console.log("Should be real: " + fake_module.foo());

mockery.registerMock('./fixtures/fake_module', mock_fake_module);
mockery.enable();

fake_module = require('./fixtures/fake_module');
console.log("Should be mock: " + fake_module.foo());

mockery.disable();
mockery.deregisterAll();

fake_module = require('./fixtures/fake_module');
console.log("Should be real: " + fake_module.foo());