public/core/Get-MtHtmlReport.ps1

function Get-MtHtmlReport {
    <#
    .Synopsis
    Generates a formatted html report using the MaesterResults object created by ConvertTo-MtMaesterResult

    .Description
    The generated html is a single file that provides a visual representation of the test
    results with a summary view and click through of the details.

    .Example
    $pesterResults = Invoke-Pester -PassThru
    $maesterResults = ConvertTo-MtMaesterResult $pesterResults
    $output = Get-MtHtmlReport -MaesterResults $maesterResults
    $output | Out-File -FilePath $out.OutputHtmlFile -Encoding UTF8

    This example shows how to generate the html report and save it to a file by using Invoke-Pester

    .Example
    $maesterResults = Invoke-Maester -PassThru
    $output = Get-MtHtmlReport -MaesterResults $maesterResults
    $output | Out-File -FilePath $out.OutputHtmlFile -Encoding UTF8

    This example shows how to generate the html report and save it to a file by using Invoke-Maester

    .LINK
    https://maester.dev/docs/commands/Get-MtHtmlReport
    #>

    [CmdletBinding()]
    param(
        # The Maester test results returned from `Invoke-Pester -PassThru | ConvertTo-MtMaesterResult`
        [Parameter(Mandatory = $true, Position = 0)]
        [psobject] $MaesterResults
    )

    Write-Verbose "Generating HTML report."
    $json = $MaesterResults | ConvertTo-Json -Depth 3 -WarningAction Ignore

    $htmlFilePath = Join-Path -Path $PSScriptRoot -ChildPath '../../assets/ReportTemplate.html'
    $templateHtml = Get-Content -Path $htmlFilePath -Raw

    # Insert the test results json into the template.
    # Locate the EndOfJson sentinel (handles both double-quote and backtick strings
    # produced by different Vite/Rolldown versions) then walk back to the variable
    # assignment that owns the placeholder object so the same variable name is preserved.
    $endPattern = 'EndOfJson:(?:"EndOfJson"|`EndOfJson`)\}'
    $endMatch = [regex]::Match($templateHtml, $endPattern)
    $insertLocationEnd = $endMatch.Index + $endMatch.Length

    # Find the last variable declaration (var/const/let NAME=) before the end marker.
    $startMatches = [regex]::Matches($templateHtml.Substring(0, $endMatch.Index), '(?:var|const|let)\s+\w+\s*=')
    $startMatch = $startMatches[$startMatches.Count - 1]
    $insertLocationStart = $startMatch.Index + $startMatch.Value.Length  # position just after the '='

    $outputHtml = $templateHtml.Substring(0, $insertLocationStart)
    $outputHtml += $json
    $outputHtml += $templateHtml.Substring($insertLocationEnd)

    return $outputHtml
}