fix(exporter): fix unit tests

aspnet-core/framework/exporter/LINGYUN.Abp.Exporter.Pdf.LibreOffice/LINGYUN/Abp/Exporter/Pdf/LibreOffice/AbpExporterPdfLibreOfficeModule.cs

@@ -8,6 +8,11 @@ public class AbpExporterPdfLibreOfficeModule : AbpModule
 {
     public override void ConfigureServices(ServiceConfigurationContext context)
     {
+        // 解决单元测试问题
+        if (context.Services.IsAdded<LibreOfficeTestEnvironment>())
+        {
+            return;
+        }
         if (!LibreOfficeCommands.IsLibreOffliceInstalled())
         {
             throw new Volo.Abp.AbpInitializationException("Libreoffice not installed in the current operation environment of the host, please refer to the document after installation using ` AbpExporterPdfLibreOfficeModule ` module.");

aspnet-core/framework/exporter/LINGYUN.Abp.Exporter.Pdf.LibreOffice/LINGYUN/Abp/Exporter/Pdf/LibreOffice/LibreOfficeTestEnvironment.cs

@@ -0,0 +1,4 @@
+namespace LINGYUN.Abp.Exporter.Pdf.LibreOffice;
+public class LibreOfficeTestEnvironment
+{
+}

aspnet-core/framework/exporter/LINGYUN.Abp.Exporter.Pdf/LINGYUN/Abp/Exporter/Pdf/NullExcelToPdfProvider.cs → aspnet-core/framework/exporter/LINGYUN.Abp.Exporter.Pdf/LINGYUN/Abp/Exporter/Pdf/OriginalExcelToPdfProvider.cs

@@ -6,11 +6,10 @@ using Volo.Abp.DependencyInjection;
 namespace LINGYUN.Abp.Exporter.Pdf;
 
 [Dependency(TryRegister = true)]
-public class NullExcelToPdfProvider : IExcelToPdfProvider, ISingletonDependency
+public class OriginalExcelToPdfProvider : IExcelToPdfProvider, ISingletonDependency
 {
-    private readonly static Stream _nullStreamCache = Stream.Null;
     public virtual Task<Stream> ParseAsync(Stream excelStream, CancellationToken cancellationToken = default)
     {
-        return Task.FromResult(_nullStreamCache);
+        return Task.FromResult(excelStream);
     }
 }