GMAT club tests are very representative of the real GMAT!

There are quite a few GMAT resources in the online platforms which are very close to GMAT, GMAT club test are one of these.

There are other test series which are often tougher than GMAT, but the problem with those test series is that you are not able to gauge enough confidence about the score you are going to get in real GMAT, you can just hope about a better performance in GMAT given that the test series was tougher than GMAT.

The beautiful thing about GMAT club tests is the analysis which they put together for your test performance, and if this analysis is put to use to for strategic sectional preparation, then it can really help you boost your performance.

Generally as a rule of thumb, the score in your last 3-4 tests can act as a benchmark performance and you an expect more or less the same in real GMAT.