René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Disable NPE checks for non-public library fields","articleBody":"**Description**\r\n\r\nFor now, the engine considers method invocations or field access on null values as producing `NullPointerException`. Previously in #226 such NPE checks were disabled for final fields from library classes because it often leads to the generation of tests with exceptions that are unexpected for a user with high usage of Java reflection. It is suggested to extend such a strategy to non-public fields from library classes too, for the same reasons.\r\n\r\n**Expected behavior**\r\n\r\nConsider generating tests for such a method:\r\n```java\r\npublic class DateExample {\r\n    boolean foo(Date date) {\r\n        return date.getTime() == 100;\r\n    }\r\n}\r\n```\r\n\r\nOnly such 3 tests are expected by user:\r\n```java\r\n@Test\r\n@DisplayName(\"foo: return date.getTime() == 100 : False -\u003e return date.getTime() == 100\")\r\npublic void testFoo_DateGetTimeNotEquals100() {\r\n    DateExample dateExample = new DateExample();\r\n    Date date = new Date(-155L);\r\n\r\n    boolean actual = dateExample.foo(date);\r\n\r\n    assertFalse(actual);\r\n}\r\n\r\n@Test\r\n@DisplayName(\"foo: return date.getTime() == 100 : True -\u003e return date.getTime() == 100\")\r\npublic void testFoo_DateGetTimeEquals100() {\r\n    DateExample dateExample = new DateExample();\r\n    Date date = new Date(100L);\r\n\r\n    boolean actual = dateExample.foo(date);\r\n\r\n    assertTrue(actual);\r\n}\r\n\r\n@Test\r\n@DisplayName(\"foo: return date.getTime() == 100 : True -\u003e ThrowNullPointerException\")\r\npublic void testFoo_DateGetTime() {\r\n    DateExample dateExample = new DateExample();\r\n\r\n    assertThrows(NullPointerException.class, () -\u003e dateExample.foo(null));\r\n}\r\n```\r\n\r\nBut for now, UtBot also generates at least 2 such tests:\r\n```java\r\n@Test\r\n@DisplayName(\"foo: return date.getTime() == 100 : True -\u003e ThrowNullPointerException\")\r\npublic void testFoo_ThrowNullPointerException() throws Exception {\r\n    DateExample dateExample = new DateExample();\r\n    Date date = ((Date) createInstance(\"java.util.Date\"));\r\n    Object immutableGregorianDate = createInstance(\"sun.util.calendar.ImmutableGregorianDate\");\r\n    setField(immutableGregorianDate, \"date\", null);\r\n    setField(date, \"cdate\", immutableGregorianDate);\r\n\r\n    assertThrows(NullPointerException.class, () -\u003e dateExample.foo(date));\r\n}\r\n\r\n@Test\r\n@DisplayName(\"foo: return date.getTime() == 100 : True -\u003e ThrowNullPointerException\")\r\npublic void testFoo_ThrowNullPointerException_1() throws ClassNotFoundException, Exception {\r\n    Class dateClazz = Class.forName(\"java.util.Date\");\r\n    BaseCalendar prevGcal = ((BaseCalendar) getStaticFieldValue(dateClazz, \"gcal\"));\r\n    BaseCalendar prevJcal = ((BaseCalendar) getStaticFieldValue(dateClazz, \"jcal\"));\r\n    try {\r\n        setStaticField(dateClazz, \"gcal\", null);\r\n        setStaticField(dateClazz, \"jcal\", null);\r\n        DateExample dateExample = new DateExample();\r\n        Date date = ((Date) createInstance(\"java.util.Date\"));\r\n        Object immutableGregorianDate = createInstance(\"sun.util.calendar.ImmutableGregorianDate\");\r\n        LocalGregorianCalendar.Date date1 = ((LocalGregorianCalendar.Date) createInstance(\"sun.util.calendar.LocalGregorianCalendar$Date\"));\r\n        setField(date1, \"zoneinfo\", null);\r\n        setField(date1, \"normalized\", false);\r\n        setField(date1, \"millis\", 0);\r\n        setField(date1, \"seconds\", 0);\r\n        setField(date1, \"minutes\", 0);\r\n        setField(date1, \"hours\", 0);\r\n        setField(date1, \"dayOfMonth\", 0);\r\n        setField(date1, \"month\", 0);\r\n        setField(date1, \"gregorianYear\", 11564545);\r\n        setField(immutableGregorianDate, \"date\", date1);\r\n        setField(date, \"cdate\", immutableGregorianDate);\r\n\r\n        dateExample.foo(date);\r\n    } finally {\r\n        setStaticField(Date.class, \"gcal\", prevGcal);\r\n        setStaticField(Date.class, \"jcal\", prevJcal);\r\n    }\r\n}\r\n```\r\n\r\nThese tests SHOULD NOT be generated (in the plugin, at least).\r\n\r\n**Environment**\r\n\r\nNo mocks, Java.\r\n\r\n**Potential alternatives**\r\n\r\nUnknown.\r\n\r\n**Context**\r\n\r\nWe can possibly lose some branches with such disabling.\r\n","author":{"url":"https://github.com/Damtev","@type":"Person","name":"Damtev"},"datePublished":"2022-06-30T10:05:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/358/UTBotJava/issues/358"}