test(Dropdown): add unit test improve code coverage

[ArgoZhang]

add unit test improve code coverage

Summary of the changes (Less than 80 chars)

简单描述你更改了什么, 不超过80个字符；如果有关联 Issue 请在下方填写相关编号

Description

fixes #5320

Regression?

• Yes
• No

[If yes, specify the version the behavior has regressed from]

[是否影响老版本]

Risk

• High
• Medium
• Low

[Justify the selection above]

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• Merge the latest code from the main branch

Summary by Sourcery

Tests:

• Added unit tests for the Dropdown component.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request adds unit tests to improve code coverage for the Dropdown component's split button functionality and updates the markup implementation to enhance clarity and functionality.

Sequence Diagram for Dropdown Split Button Test

sequenceDiagram
    actor Tester as UnitTest
    participant Dropdown as Dropdown Component
    participant DynamicElement as Rendered DynamicElement

    Tester->>Dropdown: Simulate click on split button
    Dropdown->>DynamicElement: Render <DynamicElement TagName="button">
    DynamicElement-->>Dropdown: Trigger OnClick event
    Dropdown-->>Tester: Handle click event & update state

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File-Level Changes

Change	Details	Files
Extended test implementation for Dropdown's split button functionality.	Changed the test method implementation to be asynchronous. Added callback functions for OnClick and OnClickWithoutRender events. Inserted assertions to verify that both callbacks are correctly triggered when the button is clicked.	test/UnitTest/Components/DropdownTest.cs
Modified the Dropdown component markup for the button element.	Updated the DynamicElement instantiation by adding the TagName attribute for better semantic clarity. Preserved configurable attributes such as type, class, data-bs-toggle, and disabled state.	src/BootstrapBlazor/Components/Dropdown/Dropdown.razor

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#5320	Update unit tests for Dropdown component to improve code coverage	✅

Possibly linked issues

• test(Dropdown): update unit test improve code coverage #5320: The PR fixes the issue by updating the dropdown component.
• test(Dropdown): update unit test improve code coverage #5320: The PR fixes the issue by updating the Dropdown component and adding a unit test to cover the scenario.

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[sourcery-ai]

Hey @ArgoZhang - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (49454b1) to head (91dcd71).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #5323   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          644       644           
  Lines        28922     28934   +12     
  Branches      4111      4113    +2     
=========================================
+ Hits         28922     28934   +12     

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