Definitely not a "replacement" for testosterone. You could probably get away with using it without test for some extent of of time but it will catch up with you.
Eq, just as with almost any anabolic steroids, will cause suppression of your endogenous hormones, such as endogenous LH, FSH, and testosterone. Typically, as exogenous androgen levels rise, endogenous (natural) levels fall. This is why Eq is almost never used alone, and some form of injectable testosterone is the most common addition to a cycle where Eq is being used.