What are common pitfalls or gotchas with subtesting and table-driven tests?

When writing subtests and table-driven tests in Perl, developers often encounter several common pitfalls or gotchas that can lead to confusion and test failures. Here are some of the key issues to watch out for:

  • Subtest Output Confusion: Subtests can make it difficult to track which tests are failing if the output isn't clear. Always ensure your subtest descriptions are concise and informative.
  • Data Leakage: When using table-driven tests, ensure that test data does not affect subsequent tests. Isolate test data properly to avoid unexpected results.
  • Order Dependency: Make sure your tests do not rely on the order in which they are run. Each test should be self-contained to avoid flaky tests.
  • Missing Data Validation: Validate input data before running tests. This can help catch issues early in subtests, particularly in table-driven tests where multiple inputs are tested.
  • Incorrect Test Counts: Be mindful of the number of tests being reported, especially in subtests. If a subtest fails, it may not increment the count as expected, leading to misleading outputs.

Example of Subtest and Table-Driven Test

use Test::More; subtest 'Calculation Tests' => sub { my @tests = ( { input => [1, 2], expected => 3 }, { input => [4, 5], expected => 9 }, ); foreach my $test (@tests) { my $result = sum(@{$test->{input}}); is($result, $test->{expected}, "Sum of @$test->{input} should be $test->{expected}"); } }; done_testing();

subtests table-driven tests Perl testing pitfalls test failures test output test isolation

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