See test:
test/langtools/jdk/javadoc/doclet/testModules/TestModules.java

When run with JavadocTester checkLinks, it reports two different issues in one test case:


Starting subtest 1.1: Check links
out-aggregatorModuleSummary/moduleT/module-summary.html:163: name already declared: searchphrase
Missing files: (1)
out-aggregatorModuleSummary/overview-frame.html
    in out-aggregatorModuleSummary/module-overview-frame.html
    in out-aggregatorModuleSummary/moduleA/module-frame.html
    in out-aggregatorModuleSummary/moduleB/module-frame.html
    in out-aggregatorModuleSummary/moduleT/module-frame.html
  Checked 24 files.
  Found 369 references to 67 anchors in 27 files and 0 other URIs.
* 1 missing files
* 1 duplicate ids
       0 missing ids