why empty coverage

appveyor.yml

@@ -130,6 +130,8 @@ test_script:
     - ps: >-
         If ($env:BUILD_PLATFORM -Match "x86") {
             Write-Host "Running phpt tests via OpenCppCoverage..."
+            dir $env:PHP_SRC_DIR\*sqlsrv
+            dir .\*sqlsrv*.dll
             OpenCppCoverage.exe --sources $env:PHP_SRC_DIR\sqlsrv --sources $env:PHP_SRC_DIR\pdo_sqlsrv --modules .\php_sqlsrv.dll --modules .\php_pdo_sqlsrv.dll --export_type=cobertura:.\coverage.xml --quiet --cover_children --continue_after_cpp_exception --optimized_build -- .\php.exe run-tests.php -P ${env:APPVEYOR_BUILD_FOLDER}\test\functional\ | out-file -filePath ${env:APPVEYOR_BUILD_FOLDER}\test\functional\tests.log -encoding UTF8;
             Write-Host "Showing the last 25 lines of the log file..."
             Get-Content ${env:APPVEYOR_BUILD_FOLDER}\test\functional\tests.log -Tail 25;