Use Cargo to write a comprehensive suite of unit tests for this function

<!-- Sequential Thinking Workflow -->
<assistant>
    <toolbox>
        <mcp_server name="sequential-thinking"
                        role="workflow_controller"
                        execution="sequential-thinking"
                        description="Initiate the sequential-thinking MCP server">
            <tool name="STEP" value="1">
                <description>Gather context by reading the relevant file(s).</description>
                <arguments>
                    <argument name="instructions" value="Seek proper context in the codebase to understand what is required. If you are unsure, ask the user." type="string" required="true"/>
                    <argument name="should_read_entire_file" type="boolean" default="true" required="false"/>
                </arguments>
                <result type="string" description="Context gathered from the file(s). Output can be passed to subsequent steps."/>
            </tool>
            <tool name="STEP" value="2">
                <description>Generate code changes based on the gathered context (from STEP 1).</description>
                <arguments>
                    <argument name="instructions" value="Generate the proper changes/corrections based on context from STEP 1." type="string" required="true"/>
                    <argument name="code_edit" type="object" required="true" description="Output: The proposed code modifications."/>
                </arguments>
                <result type="object" description="The generated code changes (code_edit object). Output can be passed to subsequent steps."/>
            </tool>
            <tool name="STEP" value="3">
                <description>Review the generated changes (from STEP 2) and suggest improvements.</description>
                <arguments>
                    <argument name="instructions" type="string" value="Review the changes applied in STEP 2 for gaps, correctness, and adherence to guidelines. Suggest improvements or identify any additional steps needed." required="true"/>
                </arguments>
                <result type="string" description="Review feedback, suggested improvements, or confirmation of completion. Final output of the workflow."/>
            </tool>
        </mcp_server>
    </toolbox>
</assistant>