Fix unit test for String.Format()

[josesimoes]

Description

• Now expecting ArgumentNullException.
• Improve IntelliSense comment to include ArgumentNullException.

Motivation and Context

• Fixes expected exception to follow .NET behaviour.
• Related with Support for generics <T> Home#782.

How Has This Been Tested?

• Unit tests running at Various fixes for generics support nf-interpreter#3338.
• [tested against nanoclr buildId 61048]

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue with code or algorithm)
• New feature (non-breaking change which adds functionality to code)
• Breaking change (fix or feature that would cause existing functionality to change)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dependencies (update dependencies and changes associated, has no impact on code or features)
• Unit Tests (add new Unit Test(s) or improved existing one(s), has no impact on code or features)
• Documentation (changes or updates in the documentation, has no impact on code or features)

Checklist:

• My code follows the code style of this project (only if there are changes in source code).
• My changes require an update to the documentation (there are changes that require the docs website to be updated).
• I have updated the documentation accordingly (the changes require an update on the docs in this repo).
• I have read the CONTRIBUTING document.
• I have tested everything locally and all new and existing tests passed (only if there are changes in source code).
• I have added new tests to cover my changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes update String.Format method behavior documentation and align unit tests to reflect that ArgumentNullException is thrown when a null format string argument is provided, rather than NullReferenceException.

Changes

Cohort / File(s)	Summary
Test Exception Expectation Tests/NFUnitTestArithmetic/UnitTestFormat.cs	Updated StringFormat_01 test to expect ArgumentNullException instead of NullReferenceException when format string is null.
API Documentation nanoFramework.CoreLibrary/System/String.cs	Added ArgumentNullException exception tag to XML documentation for String.Format method.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing a unit test for String.Format(), which directly relates to the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description clearly explains the changes: updating unit tests to expect ArgumentNullException and improving XML documentation comments to match .NET behavior.

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[josesimoes]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@nanoFramework.CoreLibrary/System/String.cs`:
- Line 718: The XML doc for the String APIs contains a stray double quote after
the closing </exception> tag (in System.String docs around String.cs) which
breaks generated docs; edit the XML comment to remove the trailing '"' so the
</exception> tag ends cleanly and ensure the surrounding <exception> entry for
parameters "format" and "args" remains well-formed (no other stray characters)
in the String class documentation.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: nanoframework/coderabbit/.coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: ab6bdfd0-6303-4b5d-bb6a-7afcfd0a8793

📥 Commits

Reviewing files that changed from the base of the PR and between c326223 and 006dce8.

📒 Files selected for processing (2)

• Tests/NFUnitTestArithmetic/UnitTestFormat.cs
• nanoFramework.CoreLibrary/System/String.cs

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud