Oblitirate test flakiness

[Wondertan]

Fixes #683
Fixes #467

Also, #736 did a good job for us and:
Closes #582
Closes #608
Hopefully closes #584
Hopefully closes #579

Bonus: #476
(it does not really fix this #476, but it fixes the flakeyness that was mixed up with #476, while #476 is another one that was not reproduced for a long time, and I assume it is now fixed)

[Wondertan]

And to be honest. We are fixing tests and wasting time on tests with zero value to the code coverage.

[codecov-commenter]

Codecov Report

Merging #756 (07114e4) into main (7997a44) will increase coverage by 0.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #756      +/-   ##
==========================================
+ Coverage   52.67%   52.85%   +0.18%     
==========================================
  Files         116      116              
  Lines        6574     6574              
==========================================
+ Hits         3463     3475      +12     
+ Misses       2748     2740       -8     
+ Partials      363      359       -4     

Impacted Files	Coverage Δ
core/testing.go	83.14% <ø> (ø)
header/p2p/server.go	56.52% <0.00%> (+3.26%)	⬆️
fraud/bad_encoding.go	34.44% <0.00%> (+3.33%)	⬆️
header/core/listener.go	58.49% <0.00%> (+5.66%)	⬆️
header/verify.go	81.39% <0.00%> (+6.97%)	⬆️

---

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[Wondertan]

I rerun tests 3 times already, and all of them pass

[Wondertan]

Forth run, one guy failed, fixing him

[Wondertan]

Ok, 3 more times, and it passes. Should be enough

[Bidon15]

🚢 🚢 🚢 🚢
yes yes yes yes

[renaynay]

MORGE IT

[Wondertan]

[Wondertan]

Ok, I accidentally pushed runtime.GOMAXPROCS(1), which fixed heightSub on CI completely, but it is cheating

[Wondertan]

With some runtime tricks I was able tor reproduce and fix all the flakes, but this one is not and it makes me insane

[liamsi]

ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)

maybe try increasing the timeout there? I think if we rely on timeouts we will always run into some flakines no?

[liamsi]

Changes look gud

[Wondertan]

The test does not fail because of the timeout. It fails because, for some reason, one test routine is executed after the background routine.

maybe try increasing the timeout there? I think if we rely on timeouts we will always run into some flakines no?

I put global timeouts in general for tests with concurrency. If they deadlock for some flakey or other reason.

[Wondertan]

I think the heightSub test is fixed forever with the time sleep. However #579 showed up again lol

[Wondertan]

I ran CI 6 times and on the seventh time, it failed with something I didn't see before.

[Wondertan]

#759 But it is unrelated to this PR so I am merging this