diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a22c8d50c8..f0fb8503d1 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -117,7 +117,7 @@ jobs:
     - name: Upgrade Pip.
       run: |
         python -m ensurepip --upgrade
-    - name: Test Pip.
+    - name: Test Pip
       run: |
         pip --version
     - name: Install Antlr tool
@@ -162,7 +162,13 @@ jobs:
             $Before = "${{ github.event.before }}"
             $After = "${{ github.event.after }}"
         }
-        _scripts/test.ps1 -target ${{ matrix.language }} -pc "$Before" -cc "$After"
+        if ("${{ matrix.os }}" -eq "ubuntu-latest") {
+            _scripts/test.ps1 -target ${{ matrix.language }} -pc "$Before" -cc "$After"
+        } elseif ("${{ matrix.os }}" -eq "windows-latest") {
+            _scripts/test.ps1 -target ${{ matrix.language }} -pc "$Before" -cc "$After"
+        } elseif ("${{ matrix.os }}" -eq "macos-latest") {
+            _scripts/test.ps1 -target ${{ matrix.language }} -pc "$Before" -cc "$After" -buildonly:1
+        }
 
   static-check:
     runs-on: ${{ matrix.os }}
diff --git a/_scripts/test.ps1 b/_scripts/test.ps1
index 8902a4a41f..4aeacc2e54 100644
--- a/_scripts/test.ps1
+++ b/_scripts/test.ps1
@@ -1,7 +1,8 @@
 param (
     [string]$target='CSharp',
     [string]$pc,
-    [string]$cc
+    [string]$cc,
+    [bool]$buildonly=$false
 )
 
 function Get-GrammarSkip {
@@ -123,22 +124,23 @@ function Test-Grammar {
         }
 
         # test
-        $start2 = Get-Date
-        Write-Host "--- Testing files ---"
-$workingDirectory = Get-Location
-Write-Host "The pwd is  $workingDirectory"
-        ./test.ps1
-        $passed = $LASTEXITCODE -eq 0
-
-        if (! $passed) {
-            $success = $false
-            $failStage = [FailStage]::Test
-            Write-Host "Test completed, time: $((Get-Date) - $start2)" -ForegroundColor Yellow
-            Set-Location $cwd
-            return @{
-                Success     = $success
-                Stage       = $failStage
-                FailedCases = $failedList
+        if (! $buildonly) {
+            $start2 = Get-Date
+            Write-Host "--- Testing files ---"
+            $workingDirectory = Get-Location
+            Write-Host "The pwd is  $workingDirectory"
+            ./test.ps1
+            $passed = $LASTEXITCODE -eq 0
+            if (! $passed) {
+                $success = $false
+                $failStage = [FailStage]::Test
+                Write-Host "Test completed, time: $((Get-Date) - $start2)" -ForegroundColor Yellow
+                Set-Location $cwd
+                return @{
+                    Success     = $success
+                    Stage       = $failStage
+                    FailedCases = $failedList
+                }
             }
         }
     }
diff --git a/bnf/README.md b/bnf/README.md
index 0a4dd6403f..6c02836e6b 100644
--- a/bnf/README.md
+++ b/bnf/README.md
@@ -16,3 +16,6 @@ https://dl.acm.org/doi/pdf/10.1145/366193.366201
 https://www.softwarepreservation.org/projects/ALGOL/paper/Backus-Syntax_and_Semantics_of_Proposed_IAL.pdf
 
 https://dl.acm.org/doi/pdf/10.1145/355588.365140
+
+### Issues
+* Grammar is ambiguous.