Add unit tests for getLinks

* Added a check for a successful linkcheck
* Added a check for a page without links
9 jobs for 25-fix-method-getlinks in 2 minutes and 56 seconds (queued for 5 minutes and 41 seconds)
Status Job ID Name Coverage
  Lint
passed #5165
lint:lint-php5.4

00:00:27

passed #5166
lint:lint-php5.6

00:00:27

passed #5167
lint:lint-php7.0

00:00:29

passed #5168
lint:lint-php7.1

00:00:31

 
  Codesniffer
passed #5169
codesniffer

00:00:35

 
  Unit
passed #5170
unit:testBasic

00:00:41

passed #5171
unit:testRead

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passed #5172
unit:testReadAssertFail

00:00:36

passed #5173
unit:testUserProperty

00:00:35