Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
I’ve tested this across 1.4.5 and 1.5.5 now, as well as across numerous different models. There seems to be an odd, fundamental misunderstanding about jest parameters. The models often seem to think that they can interchange plural parameters, when in fact the parameters are singular. I don’t know why jest doesn’t blow up with the bad params, it continues on as if they are not a problem, however they don’t work:
—testPathIgnorePatterns
Is INCORRECT! The correct param is:
–testPathIgnorePattern
Singular. When the singular form is used, the filter actually works, and you run fewer test cases. When the plural form is used, the entire set of test suites runs. I have almost 2000 tests, so I’ve written rules to govern how the agent runs tests, and even in those rules, I explain the difference between the singular (correct) and plural (incorrect) forms of the parameter. However, the models STILL use the incorrect form.
Wondering if a tweak to the system prompt or api calls might help resolve the issue here, or perhaps a built-in agent corrective procedure to just knock off the extra s when it appears. As, running 2000 tests all the time, really ■■■■■ up time.
Steps to Reproduce
In a project with many broken unit tests, instruct the agent/llm to run some subset.
They will often run with the plural parameter (inconsistently, they seem to think the params are interchangeable.)
Weep when your monster test suite runs fully every time, again and again, while fixing tests.
Expected Behavior
Correct name of parameter (for any terminal command, really) should always be used. Models are non-deterministic, but this is not something that should be non-deterministic.
Operating System
MacOS
Current Cursor Version (Menu → About Cursor → Copy)
Version: 1.5.5 (Universal)
VSCode Version: 1.99.3
Commit: 823f58d4f60b795a6aefb9955933f3a2f0331d70
Date: 2025-08-25T17:40:25.290Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.5.0