Run the tests solution wide, locally and in CI

.github/workflows/build.yml

@@ -53,34 +53,9 @@ jobs:
       - name: Build
         run: dotnet build src --configuration Release ${{ env.VERSION_ARGUMENT }}
 
-      # One project at a time, deleting the LocalDB instances in between, as each project
-      # creates its own and they collide when left behind.
+      # The whole solution in one run, with the test projects in parallel, as a developer runs it.
       - name: Test
-        shell: pwsh
-        run: |
-          $projects = @(
-            'LocalDb.Tests'
-            'EfClassicLocalDb.Tests'
-            'EfLocalDb.Tests'
-            'EfLocalDb.NUnit.Tests'
-            'EfLocalDb.MSTest.Tests'
-            'EfLocalDb.Xunit.V3.Tests'
-            'EfLocalDb.TUnit.Tests'
-          )
-          $failed = @()
-          foreach ($project in $projects)
-          {
-            dotnet test --project "src/$project" --configuration Release --no-build --no-restore
-            if ($LASTEXITCODE -ne 0)
-            {
-              $failed += $project
-            }
-            sqllocaldb info | ForEach-Object { sqllocaldb stop $_ ; sqllocaldb delete $_ }
-          }
-          if ($failed.Count -gt 0)
-          {
-            throw "Failed test projects: $($failed -join ', ')"
-          }
+        run: dotnet test --solution src/LocalDb.slnx --configuration Release --no-build --no-restore
 
       - name: Upload received on failure
         if: failure()

src/EfLocalDb.ReportTrxHelper/Directory.Build.targets

@@ -0,0 +1,18 @@
+<Project>
+  <!--
+    This executable hosts no tests. ReportTrxGuardTests launches it to prove a guard, and nothing
+    else should run it.
+
+    Under Microsoft.Testing.Platform, dotnet test decides what to run from
+    IsTestingPlatformApplication, not from IsTestProject, so IsTestProject=false in the project
+    file is not enough: a solution wide dotnet test runs this too, finds zero tests, and fails the
+    whole run with exit code 8.
+
+    It has to be set here rather than in the project file. NUnit3TestAdapter's targets assign it
+    from EnableNUnitRunner unconditionally, and package targets are imported after the project
+    file's own properties but before Directory.Build.targets.
+  -->
+  <PropertyGroup>
+    <IsTestingPlatformApplication>false</IsTestingPlatformApplication>
+  </PropertyGroup>
+</Project>

src/EfLocalDb.ReportTrxHelper/EfLocalDb.ReportTrxHelper.csproj

@@ -5,6 +5,14 @@
     <EnableNUnitRunner>true</EnableNUnitRunner>
     <IsTestProject>false</IsTestProject>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
+    <!--
+      Directory.Build.targets turns IsTestingPlatformApplication off so that dotnet test does not
+      run this. These two default to that property, and are what make this a testing platform
+      executable that accepts report-trx in the first place: the generated Main, and the
+      registration of the TRX extension.
+    -->
+    <GenerateTestingPlatformEntryPoint>true</GenerateTestingPlatformEntryPoint>
+    <GenerateSelfRegisteredExtensions>true</GenerateSelfRegisteredExtensions>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.Testing.Extensions.TrxReport" />