René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Fuzzer can't generate values (even without any modifications) when there are some modifications it fails to use","articleBody":"**Description (abstract example)**\r\n\r\nWhen using `Seed.Recursive` with modification `X` that has a parameter of type `T`, while there are no seeds for type `T`, fuzzer doesn't generate any values for that `Seed.Recursive` (except for the ones produced by its `Routine.Empty`, which is typically just `null`)\r\n\r\n**Real world (concrete) example**\r\n\r\nNo integration tests using `topicRepository.save(Topic)` modification are generated for methods of [`TopicService` class in `Medical-Web-App` project](https://github.com/MathAndMedLab/Medical-Web-App/blob/63ed67c73466eacea25e1a6335091e0e261fd535/src/main/java/com/app/medicalwebapp/services/TopicService.java) (or any other class that depends on `TopicRepository`). That happens because:\r\n1. There's `Topic.setCreationTime(LocalDateTime)` modification.\r\n2. Java fuzzer can't generate any values for `LocalDateTime` (_a separate issue_ #2437).\r\n3. Fuzzing platform fails to generate non-`null` values for `Topic` type due to point 2 and 3 (**concern of this issue**).\r\n4. Modification `topicRepository.save(Topic)` is only used with `null` values of `topic`, which causes modification itself to fail before we even get to method under test.\r\n\r\n**To Reproduce**\r\n\r\nRun the following unit test.\r\n```kotlin\r\nfun `fuzzer can generate non empty values even when it can't modify it due to lack of seeds`() {\r\n   class Type(val hasSeeds: Boolean)\r\n   class Value(val isEmpty: Boolean)\r\n\r\n   runBlocking {\r\n       withTimeout(1000) {\r\n           runFuzzing(\r\n               { _, type -\u003e\r\n                   if (type.hasSeeds) sequenceOf(Seed.Recursive(\r\n                       construct = Routine.Create(emptyList()) { Value(isEmpty = false) },\r\n                       modify = sequenceOf(Routine.Call(listOf(Type(hasSeeds = false))) { _, _ -\u003e\r\n                           fail(\"Value is generated for type with no seeds\")\r\n                       }),\r\n                       empty = Routine.Empty { Value(isEmpty = true) }\r\n                   ))\r\n                   else emptySequence()\r\n               },\r\n               Description(listOf(Type(hasSeeds = true)))\r\n           ) { _, (value) -\u003e\r\n               if (value.isEmpty) BaseFeedback(result = Unit, Control.CONTINUE)\r\n               else BaseFeedback(result = Unit, Control.STOP)\r\n           }\r\n       }\r\n   }\r\n}\r\n```\r\n\r\n**Expected behavior**\r\n\r\nTest passes.\r\n\r\n**Actual behavior**\r\n\r\nTest fails.\r\n\r\n**Visual proofs (screenshots, logs, images)**\r\n\r\n```\r\nTimed out waiting for 1000 ms\r\nkotlinx.coroutines.TimeoutCancellationException: Timed out waiting for 1000 ms\r\n    (Coroutine boundary)\r\n    at org.utbot.fuzzing.FuzzerSmokeTest$fuzzer can generate non empty values even when it can't modify it due to lack of seeds$1.invokeSuspend(FuzzerSmokeTest.kt:445)\r\nCaused by: kotlinx.coroutines.TimeoutCancellationException: Timed out waiting for 1000 ms\r\n    at app//kotlinx.coroutines.TimeoutKt.TimeoutCancellationException(Timeout.kt:184)\r\n    at app//kotlinx.coroutines.TimeoutCoroutine.run(Timeout.kt:154)\r\n    at app//kotlinx.coroutines.EventLoopImplBase$DelayedRunnableTask.run(EventLoop.common.kt:508)\r\n    at app//kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:284)\r\n    at app//kotlinx.coroutines.DefaultExecutor.run(DefaultExecutor.kt:108)\r\n    at java.base@19.0.2/java.lang.Thread.run(Thread.java:1589)\r\n```","author":{"url":"https://github.com/IlyaMuravjov","@type":"Person","name":"IlyaMuravjov"},"datePublished":"2023-07-20T10:56:31.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/2428/UTBotJava/issues/2428"}