Kaiyao Ke created TINKERPOP-3079:
------------------------------------
Summary: The test
`TraversalStrategiesTest#shouldAllowUserManipulationOfGlobalCache` is not
idempotent, as it passes in the first run and fails in repeated runs in the
same environment.
Key: TINKERPOP-3079
URL: https://issues.apache.org/jira/browse/TINKERPOP-3079
Project: TinkerPop
Issue Type: Bug
Environment: Ubuntu 22.04, Java 17
Reporter: Kaiyao Ke
### Brief Description of the Bug
The test `TraversalStrategiesTest#shouldAllowUserManipulationOfGlobalCache` is
non-idempotent, as it passes in the first run but fails in the second run in
the same environment. The source of the problem is that the initial strategies
registration (`StrategyA`, `StrategyB` and `StrategyC`) for the `TestGraph` and
` TestGraphComputer` classes are static (see
https://github.com/apache/tinkerpop/blob/66e5a47ffd3976d29bc7797c399b8e11c5ba810e/gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/TraversalStrategiesTest.java#L132
and
https://github.com/apache/tinkerpop/blob/66e5a47ffd3976d29bc7797c399b8e11c5ba810e/gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/TraversalStrategiesTest.java#L185).
These static blocks will only be called once during class loading.
In the first execution of the test
`TraversalStrategiesTest#shouldAllowUserManipulationOfGlobalCache`, `StrategyA`
is removed from global
strategies(https://github.com/apache/tinkerpop/blob/66e5a47ffd3976d29bc7797c399b8e11c5ba810e/gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/TraversalStrategiesTest.java#L82),
and the test does not restore it after execution.
Therefore, in the second execution of the test, `StrategyA` is not present in
the global strategies, so assertions like
`assertTrue(strategies.getStrategy(StrategyA.class).isPresent())` would
fail(https://github.com/apache/tinkerpop/blob/66e5a47ffd3976d29bc7797c399b8e11c5ba810e/gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/TraversalStrategiesTest.java#L77).
A fix is necessary since unit tests shall be self-contained. Idempotent tests
help maintain this isolation by ensuring that the state of the system under
test is consistent at the beginning of each test, regardless of previous test
runs. For example, fixing non-idempotent tests can help proactively avoid state
pollution that results in test order dependency (which could hurt regression
testing with the use of test selection / prioritization / parallelism.
### Failure Message in the 2nd Test Run:
```
java.lang.AssertionError:
at org.junit.Assert.fail(Assert.java:87)
at org.junit.Assert.assertTrue(Assert.java:42)
at org.junit.Assert.assertTrue(Assert.java:53)
at
org.apache.tinkerpop.gremlin.process.TraversalStrategiesTest.shouldAllowUserManipulationOfGlobalCache(TraversalStrategiesTest.java:77)
```
### Reproduce
Use the `NIOInspector` plugin that supports rerunning individual tests in the
same environment:
```
cd gremlin-core
mvn edu.illinois:NIOInspector:rerun
-Dtest=org.apache.tinkerpop.gremlin.process.TraversalStrategiesTest#shouldAllowUserManipulationOfGlobalCache
```
### Proposed Fix
Handle initial strategies registration in a `setup()` method rather than in
static blocks of test classes.
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