[IMPROVEMENT] Address Warnings in Tests

[smusali]

1. Understanding Warnings: Warnings are a way for the program to tell you that something might be wrong, but it's not severe enough to stop the execution of the code. However, warnings are not to be ignored as they can indicate potential problems with your code that might lead to errors under different circumstances.
2. Investigate Warnings: The first step in addressing warnings is understanding their meaning. Warning messages are often informative, pointing to the potential issue. This could be due to deprecated functions, unexpected input types, division by zero, or other reasons. Each warning should be examined in the context of the test in which it occurred to understand its cause.
3. Reproducing Warnings: To debug a warning, you need to be able to reproduce it. This means you must have a known set of conditions that consistently trigger the warning. If the warning only occurs when the tests are run as a suite and not when run individually, this could point to an issue of shared state or order dependence between tests.
4. Handling Expected Warnings: Sometimes, you might expect a warning to be produced. For example, you might have a function that issues a warning when given specific inputs. In such cases, you should use expect_warning() from the testthat package to explicitly specify that a warning is expected. This makes your intention clear to anyone reading your tests and prevents the warning from being displayed as an unexpected issue.
5. Eliminating Unnecessary Warnings: Once you've identified a warning and determined that it's not a necessary or expected part of your code's behaviour, the next step is to modify your code to prevent the warning. This could mean fixing a bug, changing your use of a specific function, or even replacing a deprecated function with its newer counterpart.
6. Testing with Different Settings: There are options to change the behaviour of warnings. Running your tests under this setting can help you catch and fix warnings you might otherwise overlook. For example, you can make all warnings error with options(warn = 2).
7. Keeping Your Code Updated: Ensure your code is updated with the latest versions of the packages you're using. Deprecated functions can cause warnings; using the latest versions can help mitigate this issue.