modify tests while maintaining coverage

This eliminates a slow test while maintaining coverage.The two tests that remain require additional terms and one needs the while loop to run while the other does not.
> drop it

The original issue identified an issue. The test need not be unnecessarily difficult to prove that the code is working. I've simply changed the requested number of terms after verifying that neither of these gives the right answer in master (at the position before where the change to the code that was added to fix the original issue took place). In addition, I've used two tests instead of 3 which cover the code added as indicated as notes on the test.