I've been given different answers to this question in different courses. Some professors say it is (using the example alternative hypothesis of $\mu > 3$):
$$H_0: \mu = 3$$ $$H_1: \mu > 3$$
Others say it is:
$$H_0: \mu \le 3$$ $$H_1: \mu > 3$$
How should I write my null hypothesis for 1-tailed tests?