Vivek Gupta created COLLECTIONS-804:
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Summary: testCollectionToArray2() is non deterministic
Key: COLLECTIONS-804
URL: https://issues.apache.org/jira/browse/COLLECTIONS-804
Project: Commons Collections
Issue Type: Bug
Components: Collection
Reporter: Vivek Gupta
The test
{{org.apache.commons.collections4.collection.AbstractCollectionTest.testCollectionToArray2()}}
can fail if two {{toArray()}} calls return elements in a different order. One
can check for that using the NonDex tool
([https://github.com/TestingResearchIllinois/NonDex]).
Bug repoduction:
# Clone the repo and cd into it.
# {{mvn test
-Dtest=org.apache.commons.collections4.bidimap.DualHashBidiMapTest#testCollectionToArray2
-Drat.skip}} This test will pass.
# {{mvn edu.illinois:nondex-maven-plugin:1.1.2:nondex
-Dtest=org.apache.commons.collections4.bidimap.DualHashBidiMapTest#testCollectionToArray2
-Drat.skip}} This command runs the NonDex tool on the the test. Near the end
of the output, you will see a summary of test failures, where you will find
{{testCollectionToArray2()}} function listed.
The source of the bug:
The test gets an array representation of the collections and then compares
them, taking the order into account. However, Java Collections need not be
necessarily ordered. Its member function {{toArray()}} also does not guarantee
a deterministic order of the elements in its returned list. As such, we should
ignore the order of the elements in the assertion.
Proposed fix:
We ignore the order of array lists by putting its elements into separate
multisets and then comparing those multisets for equality. Multiset is not a
part of the standard Java library. However, conveniently enough, this
repository already had an implementation of multiset called HashBags, which I
used.
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