Auto: ablegacy-10 — diagnostic counters as tags

Closes #253

scripts/e2e/test-ablegacy.ps1

@@ -29,6 +29,16 @@
 
 .PARAMETER BridgeNodeId
   NodeId at which the server publishes the Address.
+
+.PARAMETER DiagnosticsRequestCountNodeId
+  Optional NodeId for the synthetic _Diagnostics/<host>/RequestCount variable
+  emitted by AB Legacy discovery (PR ablegacy-10 / #253). When supplied, the
+  script runs the DiagnosticsRequestCount assertion: reads the user-tag
+  BridgeNodeId N times through the OPC UA server, then reads the diagnostic
+  counter and asserts the value is at least N (a probe loop or a parallel
+  client may have bumped it by more, so the comparison is `>=`). NodeId form:
+  ns=<n>;s=AbLegacy/<gateway>/_Diagnostics/RequestCount. Mirrors the
+  -SystemConnectionStatusNodeId knob on test-abcip.ps1.
 #>
 
 param(
@@ -36,7 +46,8 @@ param(
     [string]$PlcType = "Slc500",
     [string]$Address = "N7:5",
     [string]$OpcUaUrl = "opc.tcp://localhost:4840",
-    [Parameter(Mandatory)] [string]$BridgeNodeId
+    [Parameter(Mandatory)] [string]$BridgeNodeId,
+    [string]$DiagnosticsRequestCountNodeId
 )
 
 $ErrorActionPreference = "Stop"
@@ -150,5 +161,40 @@ if ($notifyLines.Count -eq 1) {
     $results += @{ Passed = $false; Reason = "deadband notify count $($notifyLines.Count)" }
 }
 
+# PR ablegacy-10 / #253 — diagnostic-counter round-trip assertion. After N reads
+# against the user-tag BridgeNodeId the auto-emitted _Diagnostics/<host>/RequestCount
+# counter must be >= N. The exact equality isn't asserted because a probe loop /
+# parallel client may have bumped the counter — the spec is "every read counts".
+if ($DiagnosticsRequestCountNodeId) {
+    Write-Header "DiagnosticsRequestCount (_Diagnostics/RequestCount from $DiagnosticsRequestCountNodeId)"
+    $diagN = 5
+    # Read the first counter snapshot to baseline; the assertion compares delta against
+    # the N OPC UA reads we issue between snapshots so a noisy probe loop doesn't
+    # invalidate the test.
+    $baselineOut = & $opcUaCli.File @($opcUaCli.PrefixArgs) `
+        @("read", "-u", $OpcUaUrl, "-n", $DiagnosticsRequestCountNodeId) 2>&1
+    $baseline = 0
+    if (($baselineOut -join "`n") -match '(\d+)') { $baseline = [int64]$Matches[1] }
+
+    for ($i = 0; $i -lt $diagN; $i++) {
+        & $opcUaCli.File @($opcUaCli.PrefixArgs) `
+            @("read", "-u", $OpcUaUrl, "-n", $BridgeNodeId) | Out-Null
+    }
+
+    $afterOut = & $opcUaCli.File @($opcUaCli.PrefixArgs) `
+        @("read", "-u", $OpcUaUrl, "-n", $DiagnosticsRequestCountNodeId) 2>&1
+    $after = 0
+    if (($afterOut -join "`n") -match '(\d+)') { $after = [int64]$Matches[1] }
+
+    $delta = $after - $baseline
+    if ($delta -ge $diagN) {
+        Write-Pass "DiagnosticsRequestCount delta $delta >= $diagN OPC UA reads"
+        $results += @{ Passed = $true }
+    } else {
+        Write-Fail "DiagnosticsRequestCount delta $delta < $diagN OPC UA reads (baseline=$baseline after=$after)"
+        $results += @{ Passed = $false; Reason = "diag delta $delta < $diagN" }
+    }
+}
+
 Write-Summary -Title "AB Legacy e2e" -Results $results
 if ($results | Where-Object { -not $_.Passed }) { exit 1 }