TestRequestMessageFromMailboxAsync from mailbox suite is flaky

[dshulyak]

Problem

Mentioned test randomly fails on CI.

--- FAIL: TestRequestMessageFromMailboxAsync (2.34s)
        Error Trace:    whisper_mailbox_test.go:92
	Error:      	Not equal: 
	            	expected: 0
	            	received: 1
--- FAIL: TestWhisperMailboxTestSuite (2.34s)
FAIL
FAIL	command-line-arguments	2.433s

Actually I can make it fail consistently with a following change:

diff --git a/e2e/whisper/whisper_mailbox_test.go b/e2e/whisper/whisper_mailbox_test.go
index 5865f1e..6e04e67 100644
--- a/e2e/whisper/whisper_mailbox_test.go
+++ b/e2e/whisper/whisper_mailbox_test.go
@@ -87,6 +87,7 @@ func (s *WhisperMailboxSuite) TestRequestMessageFromMailboxAsync() {
        s.postMessageToPrivate(rpcClient, pubkey.String(), topic.String(), hexutil.Encode([]byte("Hello world!")))
 
        //There are no messages, because it's a sender filter
+       time.Sleep(1 * time.Second)
        messages = s.getMessagesByMessageFilterId(rpcClient, messageFilterID)
        s.Require().Equal(0, len(messages))
 

Acceptance Criteria

Test passes consistently

[dshulyak]

@b00ris please take a look, as you are the author of this test

You can reproduce the error by applying diff from the PR description and then run:

go test ./e2e/whisper/whisper_mailbox_test.go -testify.m=TestRequestMessageFromMailboxAsync -network=

If you don't have time right now, please let me know and I will try to debug it myself

[dshulyak]

Failed build https://travis-ci.org/status-im/status-go/jobs/332249984

[b00ris]

@dshulyak Ok. I'll check it today.