Copy-pasted test cases instead of one parametrized test

Code that already exists: one of the ways AI coding agents bloat software, from lessloc's pattern catalog. lessloc catches it as copied-tests.

What makes copy-pasted test cases instead of one parametrized test a bad practice?

The standard that calls it a bad practice: Meszaros, xUnit Test Patterns: Test Code Duplication.

What does lessloc do about copy-pasted test cases instead of one parametrized test?

lessloc catches it as copied-tests.

• copied-tests (tier 2): Copy-pasted test cases that one table-driven test would cover.

Related patterns

The other patterns in Code that already exists:

• Reimplementing a helper the project already has: lessloc gives every session the rule: take what is already in the codebase before new code.
• Copying a rule another function owns: lessloc catches it as repeated-literal.
• Keeping old and new versions side by side: lessloc gives every session the rule: one implementation per rule.
• Rebuilding what the standard library or framework has: lessloc gives every session a rule against it and catches it as simpler and reinvented.
• A second library for a job an installed one already does: new-dependency names the library that is already installed.
• The same data shape in several layers (DTO, model, entity): copy catches identical type bodies.
• The same CSS declarations under another selector: lessloc catches it as style-copy.