--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/emsdk/test/test_path_preservation.ps1	Fri Jan 23 22:38:59 2026 -0800
@@ -0,0 +1,142 @@
+# This test installs emsdk and activates the latest toolchain using `--system` or `--permanent` flags,
+# and checks if parts of PATH are lost or overwritten. Set $env:SYSTEM_FLAG and $env:PERMANENT_FLAG to test each.
+# If no flag is provided the process/shell values are tested. See the CI file for an example.
+
+refreshenv
+
+$repo_root = [System.IO.Path]::GetDirectoryName((resolve-path "$PSScriptRoot"))
+
+$PATH_USER_BEFORE = [System.Environment]::GetEnvironmentVariable("PATH", "User")
+$PATH_MACHINE_BEFORE = [System.Environment]::GetEnvironmentVariable("PATH", "Machine")
+$PATH_Process_BEFORE = [System.Environment]::GetEnvironmentVariable("PATH", "Process")
+
+try {
+
+
+    & "$repo_root/emsdk.ps1" install latest
+
+    $esc = '--%'
+    & "$repo_root/emsdk.ps1" activate latest $esc $env:PERMANENT_FLAG $env:SYSTEM_FLAG
+
+    $PATH_USER = [System.Environment]::GetEnvironmentVariable("PATH", "User")
+    $PATH_MACHINE = [System.Environment]::GetEnvironmentVariable("PATH", "Machine")
+    $PATH_Process = [System.Environment]::GetEnvironmentVariable("PATH", "Process")
+
+    if ($env:SYSTEM_FLAG) {
+        echo "--system test............................."
+        $path_before_arr = $PATH_MACHINE_BEFORE.Split(';')
+        $path_arr = $PATH_MACHINE.Split(';')
+    }
+    elseif ($env:PERMANENT_FLAG) {
+        echo "--permanent test.........................."
+        $path_before_arr = $PATH_USER_BEFORE.Split(';')
+        $path_arr = $PATH_USER.Split(';')
+    } else {
+        echo "no flag test (shell/process).............."
+        $path_before_arr = $PATH_Process_BEFORE.Split(';')
+        $path_arr = $PATH_Process.Split(';')
+    }
+
+
+    $EMSDK_Path = $path_arr | Where-Object { $_ -like "$repo_root*" }
+    $EMSDK_NODE_Path = $path_arr | Where-Object { $_ -like "$repo_root\node*" }
+    $EMSDK_PYTHON_Path = $path_arr | Where-Object { $_ -like "$repo_root\python*" }
+    $EMSDK_JAVA_Path = $path_arr | Where-Object { $_ -like "$repo_root\java*" }
+    $EMSDK_UPSTREAM_Path = $path_arr | Where-Object { $_ -like "$repo_root\upstream\emscripten*" }
+
+    $number_of_items = $path_arr.count
+    [System.Collections.ArrayList]$rest_of_path = @()
+    Foreach ($item in $path_arr) {
+        if (
+            ($item -like "$repo_root*") -or
+            ($item -like "$repo_root\node*") -or
+            ($item -like "$repo_root\python*") -or
+            ($item -like "$repo_root\java*") -or
+            ($item -like "$repo_root\upstream\emscripten*")
+        ) {
+            echo "$item is on the PATH"
+        }
+        else {
+            $rest_of_path.add($item) | Out-Null
+        }
+    }
+
+    # compare the PATHs before activation and after activation
+    if (Compare-Object -ReferenceObject $path_before_arr -DifferenceObject $rest_of_path ) {
+        echo "Old path is ............................."
+        echo $path_before_arr
+        echo "Current rest of path is ................."
+        echo $rest_of_path
+        throw "some parts of PATH are removed"
+    }
+
+    # Compare the other untouched PATH
+    if ($env:SYSTEM_FLAG) {
+        if (Compare-Object -ReferenceObject $PATH_USER_BEFORE.Split(';') -DifferenceObject $PATH_USER.Split(';') ) {
+            echo "Old user path is ...................."
+            echo $PATH_USER_BEFORE
+            echo "Current user path is ................"
+            echo $PATH_USER
+            throw "User PATH are changed while --system had been provided"
+        }
+    }
+    elseif ($env:PERMANENT_FLAG) {
+        if (Compare-Object -ReferenceObject $PATH_MACHINE_BEFORE.Split(';') -DifferenceObject $PATH_MACHINE.Split(';') ) {
+            echo "Old machine path is.................."
+            echo $PATH_MACHINE_BEFORE
+            echo "Current machine path is.............."
+            echo $PATH_MACHINE
+            throw "MACHINE PATH are changed while --system was not provided"
+        }
+    } else {
+        if (
+            (Compare-Object -ReferenceObject $PATH_MACHINE_BEFORE.Split(';') -DifferenceObject $PATH_MACHINE.Split(';')) -or
+            (Compare-Object -ReferenceObject $PATH_MACHINE_BEFORE.Split(';') -DifferenceObject $PATH_MACHINE.Split(';'))
+        ) {
+            echo "Old machine path is.................."
+            echo $PATH_MACHINE_BEFORE
+            echo "Current machine path is.............."
+            echo $PATH_MACHINE
+            echo "Old user path is ...................."
+            echo $PATH_USER_BEFORE
+            echo "Current user path is ................"
+            echo $PATH_USER
+            throw "MACHINE/USER PATH are changed while no flag was provided"
+        }
+    }
+
+
+
+
+}
+finally {
+    # Recover pre-split PATH
+    refreshenv
+
+    [Environment]::SetEnvironmentVariable("Path", $PATH_USER_BEFORE, "User")
+    try {
+        [Environment]::SetEnvironmentVariable("Path", $PATH_MACHINE_BEFORE, "Machine")
+    }
+    catch {}
+
+    [Environment]::SetEnvironmentVariable("Path", $PATH_Process_BEFORE, "Process")
+
+    # Recover pre activation env variables
+    [Environment]::SetEnvironmentVariable("EMSDK", $null, "User")
+    [Environment]::SetEnvironmentVariable("EMSDK_NODE", $null, "User")
+    [Environment]::SetEnvironmentVariable("EMSDK_PYTHON", $null, "User")
+
+    try {
+        [Environment]::SetEnvironmentVariable("EMSDK", $null, "Machine")
+        [Environment]::SetEnvironmentVariable("EMSDK_NODE", $null, "Machine")
+        [Environment]::SetEnvironmentVariable("EMSDK_PYTHON", $null, "Machine")
+    } catch {}
+
+
+    [Environment]::SetEnvironmentVariable("EMSDK", $null, "Process")
+    [Environment]::SetEnvironmentVariable("EMSDK_NODE", $null, "Process")
+    [Environment]::SetEnvironmentVariable("EMSDK_PYTHON", $null, "Process")
+
+    refreshenv
+
+}