test: add tests for dnsPromises.lookup

[shisama]

Added tests for dnsPromises.lookup to increase coverage and test
onlookup() and onlookupall() methods.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[cjihrig]

There are already tests for these things in the internet suite. Unfortunately, those don't count toward code coverage.

[shisama]

@cjihrig Code coverage report for internal/dns/promises.js(
27/06/2018 03:26) shows lines of uncovered code.
This adds tests to cover code in onlookup() and onlookupall().

[jasnell]

CI: https://ci.nodejs.org/job/node-test-pull-request/15671/

[shisama]

@cjihrig I found the tests for these in internet. Please tell me which tests for dns should be in internet or the others. The tests in internet don't run on CI.

[cjihrig]

Generally, tests that require the Internet should be in the internet suite. Those tests are more prone to network issues, but unfortunately are not run as part of the normal CI.

[shisama]

Thanks for your reply. OK, I'll fix this.

[shisama]

@cjihrig The tests that require the Internet were removed. But tests to check error with invalid host name are remained to improve coverage. Please take a look again.

[jasnell]

CI: https://ci.nodejs.org/job/node-test-pull-request/16395/

[shisama]

@jasnell node-test-commit-freebsd fails but I think it is not related to this. I'm not sure if it will be success, but I rebased this. Would you please run CI again?

[jasnell]

freebsd re-build: https://ci.nodejs.org/job/node-test-commit-freebsd/19630/

[shisama]

@jasnell Thank you to run CI again, but it failed. I think it is related to #17849 (flaky test).

[BridgeAR]

CI https://ci.nodejs.org/job/node-test-pull-request/16694/

[refack]

Generally, tests that require the Internet should be in the internet suite. Those tests are more prone to network issues, but unfortunately are not run as part of the normal CI.

@addaleax did a wonderful job of writing a mock DNS server in common/dns.js, for example:

node/test/parallel/test-dns-resolveany.js

Line 3 in 116f6eb

const dnstools = require('../common/dns');

[addaleax]

Landed in 2118342

[joyeecheung]

The remaining test cases still rely on internet access and will fail if the DNS is hijacked by the ISP. I move them to internet in #22516

[refack]

You can finally see the improved coverage in our published report 🥇