calling assertInstanceOf on a property set in TestCase::setUp() should result in RedundantCondition

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
22/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
php
Domain
testing

Research direction

Start by reading the plugin's handling of PHPUnit assertions and the existing tests for Psalm's RedundantCondition diagnostics. The issue gives a proposed TestCase::setUp() example, but says the exact error and test case are uncertain; trace how property types flow from setUp() into test methods and determine the expected diagnostic. Done means a regression test confirms the intended behavior without introducing other errors.

Written by the indexing model from the issue text.

Description

  • if TestCase::$foo is T|null
  • and TestCase::setUp() sets TestCase::$foo to T
  • and nothing else modifies TestCase::$foo
  • then TestCase::assertInstanceOf(T::class, $this->foo) is redundant

not quite sure on the exact error/test case that should occur, but this is a vague mashup of what I'm thinking:

  Scenario: setUp resolves types
    Given I have the following code
      """
      class MyTestCase extends TestCase
      {
        /** @var \DateTime|null */
        private $date;

        /** @return void */
        public function setUp() {
          $this->date = new \DateTime();
        }

        /** @return void */
        public function testSomething() {
          $this->assertInstanceOf(\DateTime::class, $this->date);
        }
      }
      """
    When I run Psalm
    Then I see these errors
      | Type            | Message                                                                                                     |
      | RedundantConditionGivenDocblockType | Found a redundant condition when evaluating docblock-defined type $this->date and trying to reconcile type 'DateTime' to DateTime |
    And I see no other errors
Dominant language
Gherkin
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Merged PRs (30d)
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