pipeline: fix unstable unit test (#1609)

[ti-srebot]

cherry-pick #1609 to release-5.0
You can switch your code base to this Pull Request by using git-extras:

# In ticdc repo:
git pr https://github.com/pingcap/ticdc/pull/1655

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/ticdc.git pr/1655:release-5.0-cfe4dce4e883

---

What problem does this PR solve?

Fix unstable unit test found in https://github.com/pingcap/ticdc/issues/1501#issuecomment-812846556

[2021-04-02T16:20:07.344Z] [2021/04/03 00:17:07.593 +08:00] [ERROR] [pipeline.go:96] ["found error when running the node"] [name="error node"] [error="error node throw an error, index: 3"] [errorVerbose="error node throw an error, index: 3\ngithub.com/pingcap/ticdc/pkg/pipeline.(*errorNode).Receive\n\t/home/jenkins/agent/workspace/cdc_ghpr_test/go/src/github.com/pingcap/ticdc/pkg/pipeline/pipeline_test.go:197\ngithub.com/pingcap/ticdc/pkg/pipeline.(*nodeRunner).run\n\t/home/jenkins/agent/workspace/cdc_ghpr_test/go/src/github.com/pingcap/ticdc/pkg/pipeline/runner.go:60\ngithub.com/pingcap/ticdc/pkg/pipeline.(*Pipeline).driveRunner\n\t/home/jenkins/agent/workspace/cdc_ghpr_test/go/src/github.com/pingcap/ticdc/pkg/pipeline/pipeline.go:93\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1357"] [stack="github.com/pingcap/ticdc/pkg/pipeline.(*Pipeline).driveRunner\n\t/home/jenkins/agent/workspace/cdc_ghpr_test/go/src/github.com/pingcap/ticdc/pkg/pipeline/pipeline.go:96"]
[2021-04-02T16:20:07.344Z] 
[2021-04-02T16:20:07.344Z] ----------------------------------------------------------------------
[2021-04-02T16:20:07.344Z] FAIL: pipeline_test.go:288: pipelineSuite.TestPipelineThrow
[2021-04-02T16:20:07.344Z] 
[2021-04-02T16:20:07.344Z] pipeline_test.go:284:
[2021-04-02T16:20:07.344Z]     n.c.Assert(n.index, check.Equals, 6)
[2021-04-02T16:20:07.344Z] ... obtained int = 4
[2021-04-02T16:20:07.344Z] ... expected int = 6
[2021-04-02T16:20:07.344Z] 
[2021-04-02T16:20:07.344Z] pipeline_test.go:316:
[2021-04-02T16:20:07.344Z]     c.Assert(len(errs), check.Equals, 4)
[2021-04-02T16:20:07.344Z] ... obtained int = 2
[2021-04-02T16:20:07.344Z] ... expected int = 4
[2021-04-02T16:20:07.344Z] 
[2021-04-02T16:20:07.344Z] OOPS: 3 passed, 1 skipped, 1 FAILED
[2021-04-02T16:20:07.344Z] --- FAIL: TestSuite (1.12s)
[2021-04-02T16:20:07.344Z] FAIL
[2021-04-02T16:20:07.344Z] coverage: 73.3% of statements
[2021-04-02T16:20:07.344Z] FAIL	github.com/pingcap/ticdc/pkg/pipeline	1.182s

What is changed and how it works?

Add one more check for the logic that send message to closed pipeline.

Check List

Tests

• Unit test
• Integration test

Release note

• No release note

[ti-srebot]

/run-all-tests

[codecov-io]

Codecov Report

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❗ Current head 611b72e differs from pull request most recent head becfe8a. Consider uploading reports for the commit becfe8a to get more accurate results

@@               Coverage Diff                @@
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[zier-one]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• amyangfei
• leoppro

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[zier-one]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: df72b47