diff --git a/.github/workflows/Action-Test.yml b/.github/workflows/Action-Test.yml
index e39b913..8f4669f 100644
--- a/.github/workflows/Action-Test.yml
+++ b/.github/workflows/Action-Test.yml
@@ -42,3 +42,7 @@ jobs:
       - name: Run Install-PSModule regression tests
         shell: pwsh
         run: ./tests/Install-PSModule.Tests.ps1
+
+      - name: Run Import-TestData tests
+        shell: pwsh
+        run: ./tests/Import-TestData.Tests.ps1
diff --git a/src/Helpers/Helpers.psm1 b/src/Helpers/Helpers.psm1
index a4bda63..dc2bbcd 100644
--- a/src/Helpers/Helpers.psm1
+++ b/src/Helpers/Helpers.psm1
@@ -1185,3 +1185,167 @@ function Set-GitHubLogGroup {
     Write-Host '::endgroup::'
 }
 
+function Import-TestData {
+    <#
+        .SYNOPSIS
+        Exposes caller-provided TestData as environment variables for later steps in the job.
+
+        .DESCRIPTION
+        Reads the `PSMODULE_TEST_DATA` environment variable, which is expected to contain a single-line
+        JSON object with optional `secrets` and `variables` maps. Each entry is validated and written to
+        the file referenced by `GITHUB_ENV` so it becomes available as `$env:<name>` in subsequent steps
+        of the same job. Values under `secrets` are masked in the logs via `::add-mask::`; values under
+        `variables` are not. When no test data is provided the function is a no-op.
+
+        .EXAMPLE
+        Import-TestData
+
+        Reads `$env:PSMODULE_TEST_DATA` and exposes its `secrets` and `variables` entries as environment
+        variables for the following steps in the job.
+    #>
+    [CmdletBinding()]
+    param()
+
+    if ([string]::IsNullOrWhiteSpace($env:PSMODULE_TEST_DATA)) {
+        Write-Verbose 'No test data was provided by the calling workflow.'
+        return
+    }
+    if ([string]::IsNullOrWhiteSpace($env:GITHUB_ENV)) {
+        throw 'Import-TestData requires the GITHUB_ENV environment file, which is only available inside GitHub Actions.'
+    }
+    try {
+        $data = $env:PSMODULE_TEST_DATA | ConvertFrom-Json -ErrorAction Stop
+    } catch {
+        throw "The 'TestData' secret must be valid JSON with 'secrets' and/or 'variables' maps."
+    }
+    if ($null -eq $data -or $data -isnot [pscustomobject]) {
+        throw "The 'TestData' secret must be a JSON object with 'secrets' and/or 'variables' maps."
+    }
+    $allowedTopLevelKeys = @('secrets', 'variables')
+    foreach ($propertyName in $data.PSObject.Properties.Name) {
+        if ($allowedTopLevelKeys -notcontains $propertyName) {
+            throw "The 'TestData' secret only supports 'secrets' and 'variables' maps."
+        }
+    }
+    $reservedNames = @('CI', 'HOME', 'PATH', 'PWD', 'SHELL', 'PSMODULE_TEST_DATA')
+    $reservedPrefixes = @('GITHUB_', 'RUNNER_', 'ACTIONS_')
+    function Assert-EnvironmentName {
+        <#
+            .SYNOPSIS
+            Validates that a TestData key can safely be written to GITHUB_ENV.
+        #>
+        param([string] $Name)
+        if ($Name -notmatch '^[A-Za-z_][A-Za-z0-9_]*$') {
+            throw 'TestData keys must be valid environment variable names.'
+        }
+        $normalized = $Name.ToUpperInvariant()
+        if ($reservedNames -contains $normalized) {
+            throw 'TestData keys must not override reserved environment variables.'
+        }
+        foreach ($prefix in $reservedPrefixes) {
+            if ($normalized.StartsWith($prefix)) {
+                throw 'TestData keys must not override reserved environment variables.'
+            }
+        }
+    }
+    function Assert-Map {
+        <#
+            .SYNOPSIS
+            Validates that a TestData section is a JSON object map.
+        #>
+        param(
+            [object] $Map,
+            [string] $Name
+        )
+        if ($null -eq $Map) { return }
+        if ($Map -isnot [pscustomobject]) {
+            throw "The 'TestData.$Name' value must be a JSON object."
+        }
+    }
+    function Get-EnvironmentValue {
+        <#
+            .SYNOPSIS
+            Converts a scalar TestData value to an environment variable value.
+        #>
+        param(
+            [object] $Value,
+            [string] $Name
+        )
+        if ($null -eq $Value) { return '' }
+        if (
+            $Value -is [pscustomobject] -or
+            ($Value -is [System.Collections.IEnumerable] -and $Value -isnot [string])
+        ) {
+            throw "Values in 'TestData.$Name' must be scalar values."
+        }
+        return [string]$Value
+    }
+    function Add-EnvFromMap {
+        <#
+            .SYNOPSIS
+            Writes validated TestData entries to GITHUB_ENV.
+        #>
+        param(
+            [object] $Map,
+            [string] $Name,
+            [switch] $Mask
+        )
+        Assert-Map -Map $Map -Name $Name
+        if ($null -eq $Map) { return }
+        $count = 0
+        foreach ($item in $Map.PSObject.Properties) {
+            $entryName = $item.Name
+            Assert-EnvironmentName -Name $entryName
+            $value = Get-EnvironmentValue -Value $item.Value -Name $Name
+            if ($Mask) {
+                foreach ($line in ($value -split "`n")) {
+                    $line = $line.TrimEnd("`r")
+                    if ($line.Length -gt 0) {
+                        Write-Host "::add-mask::$line"
+                    }
+                }
+            }
+            do {
+                $delimiter = "GHENV_$([guid]::NewGuid().ToString('N'))"
+            } while ($value.Contains($delimiter))
+            Add-Content -Path $env:GITHUB_ENV -Value "$entryName<<$delimiter" -Encoding utf8 -ErrorAction Stop
+            Add-Content -Path $env:GITHUB_ENV -Value $value -Encoding utf8 -ErrorAction Stop
+            Add-Content -Path $env:GITHUB_ENV -Value $delimiter -Encoding utf8 -ErrorAction Stop
+            $count++
+        }
+        if ($count -gt 0) {
+            if ($Mask) {
+                Write-Host "Exposed $count secret value(s) as environment variables."
+            } else {
+                Write-Host "Exposed $count variable value(s) as environment variables."
+            }
+        }
+    }
+
+    Assert-Map -Map $data.secrets -Name 'secrets'
+    Assert-Map -Map $data.variables -Name 'variables'
+
+    $secretNames = @()
+    if ($null -ne $data.secrets) {
+        $secretNames = @($data.secrets.PSObject.Properties.Name)
+    }
+    $variableNames = @()
+    if ($null -ne $data.variables) {
+        $variableNames = @($data.variables.PSObject.Properties.Name)
+    }
+    $secretNameSet = [System.Collections.Generic.HashSet[string]]::new(
+        [System.StringComparer]::OrdinalIgnoreCase
+    )
+    foreach ($secretName in $secretNames) {
+        [void] $secretNameSet.Add($secretName)
+    }
+    foreach ($variableName in $variableNames) {
+        if ($secretNameSet.Contains($variableName)) {
+            throw 'TestData keys must not be duplicated across secrets and variables.'
+        }
+    }
+
+    Add-EnvFromMap -Map $data.secrets -Name 'secrets' -Mask
+    Add-EnvFromMap -Map $data.variables -Name 'variables'
+}
+
diff --git a/tests/Import-TestData.Tests.ps1 b/tests/Import-TestData.Tests.ps1
new file mode 100644
index 0000000..0e4a4a6
--- /dev/null
+++ b/tests/Import-TestData.Tests.ps1
@@ -0,0 +1,127 @@
+[CmdletBinding()]
+param()
+
+$ErrorActionPreference = 'Stop'
+
+$repoRoot = Split-Path -Path $PSScriptRoot -Parent
+$helpersManifestPath = Join-Path -Path $repoRoot -ChildPath 'src/Helpers/Helpers.psd1'
+$testRoot = Join-Path -Path ([System.IO.Path]::GetTempPath()) -ChildPath "Import-TestData-$([guid]::NewGuid())"
+
+$assert = {
+    param(
+        [bool] $Condition,
+        [string] $Message
+    )
+
+    if (-not $Condition) {
+        throw $Message
+    }
+}
+
+$assertThrows = {
+    param(
+        [scriptblock] $ScriptBlock,
+        [string] $Pattern,
+        [string] $Message
+    )
+
+    $threw = $false
+    try {
+        & $ScriptBlock 6> $null
+    } catch {
+        $threw = $_.Exception.Message -like $Pattern
+    }
+    if (-not $threw) {
+        throw $Message
+    }
+}
+
+$originalTestData = $env:PSMODULE_TEST_DATA
+$originalGitHubEnv = $env:GITHUB_ENV
+
+try {
+    New-Item -Path $testRoot -ItemType Directory -Force | Out-Null
+
+    Remove-Module -Name Helpers -Force -ErrorAction SilentlyContinue
+    Import-Module -Name $helpersManifestPath -Force
+
+    $githubEnvPath = Join-Path -Path $testRoot -ChildPath 'github_env'
+
+    # Secrets and variables are written to GITHUB_ENV, and nothing leaks to the success/pipeline stream.
+    Set-Content -Path $githubEnvPath -Value '' -NoNewline -Encoding utf8
+    $env:GITHUB_ENV = $githubEnvPath
+    $env:PSMODULE_TEST_DATA = '{"secrets":{"MY_SECRET":"not-a-real-secret"},"variables":{"MY_VARIABLE":"plain-text-value"}}'
+
+    $pipelineOutput = Import-TestData 3> $null 4> $null 5> $null 6> $null
+
+    & $assert ($null -eq $pipelineOutput) 'Import-TestData must not write workflow commands or status messages to the success/pipeline output stream.'
+
+    $envContent = Get-Content -Path $githubEnvPath -Raw
+    & $assert ($envContent -match 'MY_SECRET<<') 'Expected the secret to be written to GITHUB_ENV using heredoc syntax.'
+    & $assert ($envContent -like '*not-a-real-secret*') 'Expected the secret value to be written to GITHUB_ENV.'
+    & $assert ($envContent -match 'MY_VARIABLE<<') 'Expected the variable to be written to GITHUB_ENV using heredoc syntax.'
+    & $assert ($envContent -like '*plain-text-value*') 'Expected the variable value to be written to GITHUB_ENV.'
+
+    # The mask command is emitted on the information stream (never the success stream).
+    Set-Content -Path $githubEnvPath -Value '' -NoNewline -Encoding utf8
+    $env:PSMODULE_TEST_DATA = '{"secrets":{"MY_SECRET":"not-a-real-secret"}}'
+    $information = Import-TestData 6>&1 | Out-String
+    & $assert ($information -match '::add-mask::not-a-real-secret') 'Expected the secret to be masked via ::add-mask:: on the information stream.'
+
+    # A no-op when no test data is provided; nothing on the success/pipeline stream.
+    $env:PSMODULE_TEST_DATA = ''
+    $noopOutput = Import-TestData 3> $null 4> $null 5> $null 6> $null
+    & $assert ($null -eq $noopOutput) 'The no-op path must not emit anything to the success/pipeline output stream.'
+
+    # Representative validation failure paths.
+    $env:GITHUB_ENV = $githubEnvPath
+
+    $env:PSMODULE_TEST_DATA = 'not-json'
+    & $assertThrows { Import-TestData } '*valid JSON*' 'Expected invalid JSON to be rejected.'
+
+    $env:PSMODULE_TEST_DATA = '{"unexpected":{"A":"1"}}'
+    & $assertThrows { Import-TestData } "*only supports 'secrets' and 'variables'*" 'Expected unknown top-level keys to be rejected.'
+
+    $env:PSMODULE_TEST_DATA = '{"variables":{"1INVALID":"x"}}'
+    & $assertThrows { Import-TestData } '*valid environment variable names*' 'Expected invalid env var names to be rejected.'
+
+    $env:PSMODULE_TEST_DATA = '{"variables":{"GITHUB_TOKEN":"x"}}'
+    & $assertThrows { Import-TestData } '*reserved environment variables*' 'Expected reserved env var names to be rejected.'
+
+    $env:PSMODULE_TEST_DATA = '{"secrets":{"DUP":"a"},"variables":{"DUP":"b"}}'
+    & $assertThrows { Import-TestData } '*duplicated across secrets and variables*' 'Expected duplicate keys to be rejected.'
+
+    # A non-scalar value is rejected, and the error names the section ('secrets'), not the entry key.
+    # Regression guard for the case-insensitive $name/$Name clobber in Add-EnvFromMap.
+    $env:PSMODULE_TEST_DATA = '{"secrets":{"MY_SECRET":[1,2]}}'
+    & $assertThrows { Import-TestData } '*TestData.secrets*scalar*' 'Non-scalar value must be rejected naming the section.'
+
+    # A failed write to GITHUB_ENV is terminating even when the caller's ErrorActionPreference is Continue.
+    $env:PSMODULE_TEST_DATA = '{"variables":{"MY_VARIABLE":"plain-text-value"}}'
+    $env:GITHUB_ENV = Join-Path -Path $testRoot -ChildPath 'missing-dir/github_env'
+    $previousEap = $ErrorActionPreference
+    $ErrorActionPreference = 'Continue'
+    try {
+        & $assertThrows { Import-TestData } '*missing-dir*' 'Expected an unwritable GITHUB_ENV path to raise a terminating error.'
+    } finally {
+        $ErrorActionPreference = $previousEap
+    }
+
+    # Missing GITHUB_ENV fails fast with a clear message instead of a generic parameter-binding error.
+    $env:PSMODULE_TEST_DATA = '{"variables":{"MY_VARIABLE":"plain-text-value"}}'
+    $env:GITHUB_ENV = ''
+    $clearError = $false
+    try {
+        Import-TestData 6> $null
+    } catch {
+        $clearError = $_.Exception.Message -like '*GITHUB_ENV*'
+    }
+    & $assert $clearError 'Expected a clear error mentioning GITHUB_ENV when the environment file is not available.'
+} finally {
+    $env:PSMODULE_TEST_DATA = $originalTestData
+    $env:GITHUB_ENV = $originalGitHubEnv
+    Remove-Module -Name Helpers -Force -ErrorAction SilentlyContinue
+    if (Test-Path -Path $testRoot) {
+        Remove-Item -Path $testRoot -Recurse -Force
+    }
+}