# Performing a Wald's group sequential test in R (for complex hypothesis)

The settings: we have a sequence of numbers generated from a normal distribution with $$\mu=1;\sigma^2 = 1$$. And with every new observation collected, we'd like to test for: $$H_0:\mu_0=0$$ (two-sided).

From what I've learned in school, there is the Wald's group sequential for when comparing two simple hypothesis, and I would like to know what is available for complex hypothesis.

What I am looking for is:

1. Some reference text (article/book) that describes the solution for this (or a similar) case.

2. If there is some implementation in R for performing such a test.