The test_sync integration test doesn't call on_block_imported

[tomaka]

The documentation of NetworkWorker::on_block_imported mentions that it is mandatory to call it after importing a block. However our test_sync integration test doesn't do that.

This test is extremely intricate and consists in a bunch of components glued together like spaghettis cooked for too long and without oil. I have no idea how to fix that problem, and I'd recommend rewriting the test from scratch.

At the time of opening this issue, I'm about to introduce a performance-degrading hack in the network crate to bypass this problem. Please search for this issue number in the source code after fixing it.
EDIT: #5938

[arkpar]

It is supposed to be called here:

substrate/client/network/test/src/lib.rs

Line 813 in a2512e8

peer.network.on_block_imported(

[tomaka]

I've tried running the test and print a message in on_block_imported to check whether it is called, and can confirm that it isn't.

The code used in the integration test is this one:
https://github.com/paritytech/substrate/blob/master/client/service/test/src/lib.rs

It's very redundant with the one on sc_network/test