Learn Portuguese (Portugal): O chefe tem de aprovar o produto depois de testá-lo. - The boss has to approve the product after testing it.

Because the subject (the boss) is the same for both actions. In Portuguese, when the subject doesn't change, we follow antes de and depois de with the infinitive. Also, remember that Portuguese uses the infinitive after prepositions like de, whereas English uses the -ing form (after testing).

Why did testar turn into testá-lo? Where did the letter l come from?

The word for it is the pronoun o, referring to the masculine noun o produto. When attaching o, a, os, or as to a verb ending in -r (like testar), we drop the -r and add an l to the pronoun. So, testar plus o becomes testá-lo.

Why is there an accent mark on the a in testá-lo?

Dropping the -r from an -ar verb changes how the word would naturally be stressed. To keep the stress on the final syllable where it belongs, we must add an acute accent (á).

I have sometimes seen ter que used for obligation. Why does this sentence use tem de aprovar?