Choosing the right null hypothesis

I remember from L1 that we are likely to chose the alternative hypothesis to be what we want to prove and the null hypothesis as what we want to reject which worked perfectly in one tail cases.

However, if I am an analyst that expect from previous experience that a slope b0 coefficient value to be exactly 2.5 and the regression results shows let’s say 1.3 as the value of the slope coefficient b0.

will I still have the alternative hypothesis as b0=2.5 or in this case I should assume that the regression results of 1.2 is correct and as such offer that the null hypothesis be b0=2.5?

Some of the examples i saw actually showed that the null hypothesis choice was for b0=2.5 and that the alternative that b0 not equal to 2.5.