Add parameterized module: JUnit 5 @ParameterizedTest argument sources, display names, and two real anti-pattern failures

2026-10-03 21:50:52 +00:00
parent 8be1245951
commit ee75bfa792
45 changed files with 1179 additions and 0 deletions
@@ -0,0 +1,19 @@
+Captured from a real `mvn test` run with badSharedConfigAccumulatesTouches NOT yet marked
+@Disabled -- i.e. exactly the code shape in the post's "BAD" example, run for real.
+
+-------------------------------------------------------------------------------
+Test set: com.ankurm.tutorials.junit.parameterized.SharedMutableArgumentAntiPatternTest
+-------------------------------------------------------------------------------
+Tests run: 4, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.017 s <<< FAILURE! -- in com.ankurm.tutorials.junit.parameterized.SharedMutableArgumentAntiPatternTest
+com.ankurm.tutorials.junit.parameterized.SharedMutableArgumentAntiPatternTest.badSharedConfigAccumulatesTouches(Config)[2] -- Time elapsed: 0.005 s <<< FAILURE!
+org.opentest4j.AssertionFailedError: expected: <1> but was: <2>
+	at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:569)
+	at com.ankurm.tutorials.junit.parameterized.SharedMutableArgumentAntiPatternTest.badSharedConfigAccumulatesTouches(SharedMutableArgumentAntiPatternTest.java:23)
+
+The first invocation passes (expected 1, got 1 -- the shared Config has been touched once).
+The second invocation fails with exactly the same assertion, same line number, same test
+method -- but now expects 1 and gets 2, because it is the SAME Config instance the first
+invocation already touched. Nothing about invocation 2's own code is wrong; the bug is that
+sharedProvider() built one Config and handed it to both Arguments.of(...) calls. This is
+exactly the failure mode the "fresh instance per invocation" fix in goodFreshConfigIsAlwaysTouchedOnce
+avoids -- that test passes all the way through for the identical reason this one fails.