Steps to replicate the issue (include links if applicable):

• Create a test of a function that accepts boolean input, but don't fill the input (so leave neither true neither false) - like at: https://www.wikifunctions.org/wiki/Z10191?oldid=12174
• Save the test with a missing argument value
• Open the test in an edit mode and set the missing value (to either true or false)
• Try to save

What happens?:
The test is not saved, you still have a missing argument value.

What should have happened instead?:
The new value should be saved. User should not be able to save a test with a missing argument.

A workaround is to change the function that's to be invoked to another and then back to the original one. There's no need to save in the middle.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):