adding doctests to maths/trapezoidal_rule.py

[MRJPEREZR]

Describe your change:

Contributes to #9943

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[MRJPEREZR]

Adding doctests to improve test coverage of maths/trapezoidal_rule.py from 18% to 75%.

[MRJPEREZR]

Hello @cclauss , excuse me, I was reviewing the last merged PR associated to issue #9943 and I found you as frequent reviewer to this kind of PR. I would like to know if you could help me with your approve to merge this PR. We are a group of students that we want to contribute to this project, so in the following days, it will be some others similar PR like this. Thanks.

[MRJPEREZR]

Hi @tianyizheng02,

Sorry for tagging you, but I wanted to ask if it would be possible to review and accept this PR. I know the issue is a bit old (it was opened in October 2023), but we’re a group of students working on a small project, and I thought contributing to issues like these, where tests are needed, would be valuable.

Best regards!