function foo(str)
{
    return run_func(str)
}
function run_func(str)
{
    return '1'
}
exports._test = {foo: foo, run_func: run_func}

app = require("./app.js")
describe('test', function(){
    it('test', function(){

        var foo_mock = sinon.mock(app._test)
        foo_mock.expects('run_func').withArgs('a').returns('0')
        var res = app._test.foo('a')
        assert.equal('0', res)
    })
})