diff --git a/build.proj b/build.proj
index b8ac7d44ed..c13b40e246 100644
--- a/build.proj
+++ b/build.proj
@@ -259,6 +259,20 @@
       -p:SigningKeyPath="$(SigningKeyPath)"
     </SigningKeyPathArgument>
 
+    <!--
+      TestSigningKeyPath
+      Applies to:     TestSqlClientUnit
+      Description:    Path to the key used to sign test assemblies. Required in Package mode when
+                      SigningKeyPath is set so that InternalsVisibleTo grants from signed driver
+                      assemblies can be fulfilled.
+      Default value:  [blank]
+      Example:        C:\path\to\sqlclient-test-key.snk
+    -->
+    <TestSigningKeyPath Condition="'$(TestSigningKeyPath)' == ''" />
+    <TestSigningKeyPathArgument Condition="'$(TestSigningKeyPath)' != ''">
+      -p:TestSigningKeyPath="$(TestSigningKeyPath)"
+    </TestSigningKeyPathArgument>
+
     <!--
       TestBlameTimeout
       Applies to:     Test* targets
@@ -678,10 +692,6 @@
   <!-- TestSqlClientUnit: Runs unit tests for SqlClient -->
   <Target Name="TestSqlClientUnit">
     <PropertyGroup>
-      <!--
-        Note: This test exclusively uses project references, so neither ReferenceType nor any
-            package version arguments are specified in this command.
-      -->
       <LogFilePrefix>SqlClientUnit-$(OS)</LogFilePrefix>
       <LogFilePrefix Condition="'$(TestFramework)' != ''">$(LogFilePrefix)-$(TestFramework)</LogFilePrefix>
 
@@ -692,6 +702,10 @@
         $(TestCodeCoverageArgument)
         $(TestFiltersArgument)
         $(TestFrameworkArgument)
+        $(ReferenceTypeArgument)
+        $(TestSigningKeyPathArgument)
+        $(PackageVersionSqlClientArgument)
+        $(PackageVersionSqlServerArgument)
         --results-directory "$(TestResultsFolderPath)"
         --logger:"trx;LogFilePrefix=$(LogFilePrefix)"
       </DotnetCommand>
@@ -862,7 +876,7 @@
     <PropertyGroup>
       <!--
         Note: This test exclusively uses project references, so neither ReferenceType nor any
-            package version arguments are specified in this command.
+        package version arguments are specified in this command.
       -->
       <LogFilePrefix>AbstractionsTests-$(OS)</LogFilePrefix>
       <LogFilePrefix Condition="'$(TestFramework)' != ''">$(LogFilePrefix)-$(TestFramework)</LogFilePrefix>
diff --git a/eng/pipelines/common/templates/steps/run-all-tests-step.yml b/eng/pipelines/common/templates/steps/run-all-tests-step.yml
index 5730b8cc0d..e41c7d22b2 100644
--- a/eng/pipelines/common/templates/steps/run-all-tests-step.yml
+++ b/eng/pipelines/common/templates/steps/run-all-tests-step.yml
@@ -79,51 +79,62 @@ steps:
     condition: succeededOrFailed()
 
 - ${{if eq(parameters.operatingSystem, 'Windows')}}:
-  - ${{if eq(parameters.referenceType, 'Project')}}:
-    - task: DotNetCoreCLI@2
-      displayName: 'Run Unit Tests ${{parameters.msbuildArchitecture }}'
-      condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
-      inputs:
-        command: build
-        projects: build.proj
-        ${{ if eq(parameters.msbuildArchitecture, 'x64') }}:
-          arguments: >-
-            -t:TestSqlClientUnit
-            -p:TestFramework=${{ parameters.targetFramework }}
-            -p:Configuration=${{ parameters.buildConfiguration }}
-            -p:TestResultsFolderPath=TestResults
-        ${{ else }}: # x86
-          arguments: >-
-            -t:TestSqlClientUnit
-            -p:TestFramework=${{ parameters.targetFramework }}
-            -p:Configuration=${{ parameters.buildConfiguration }}
-            -p:DotnetPath=${{ parameters.dotnetx86RootPath }}
-            -p:TestResultsFolderPath=TestResults
+  - task: DotNetCoreCLI@2
+    displayName: 'Run Unit Tests ${{parameters.msbuildArchitecture }}'
+    condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
+    inputs:
+      command: build
+      projects: build.proj
+      ${{ if eq(parameters.msbuildArchitecture, 'x64') }}:
+        arguments: >-
+          -t:TestSqlClientUnit
+          -p:TestFramework=${{ parameters.targetFramework }}
+          -p:ReferenceType=${{ parameters.referenceType }}
+          -p:Configuration=${{ parameters.buildConfiguration }}
+          -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+          -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+          -p:TestResultsFolderPath=TestResults
+      ${{ else }}: # x86
+        arguments: >-
+          -t:TestSqlClientUnit
+          -p:TestFramework=${{ parameters.targetFramework }}
+          -p:ReferenceType=${{ parameters.referenceType }}
+          -p:Configuration=${{ parameters.buildConfiguration }}
+          -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+          -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+          -p:DotnetPath=${{ parameters.dotnetx86RootPath }}
+          -p:TestResultsFolderPath=TestResults
 
-    - task: DotNetCoreCLI@2
-      displayName: 'Run Flaky Unit Tests ${{parameters.msbuildArchitecture }}'
-      condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
-      inputs:
-        command: build
-        projects: build.proj
-        ${{ if eq(parameters.msbuildArchitecture, 'x64') }}:
-          arguments: >-
-            -t:TestSqlClientUnit
-            -p:TestFramework=${{ parameters.targetFramework }}
-            -p:Configuration=${{ parameters.buildConfiguration }}
-            -p:TestFilters="category=flaky"
-            -p:TestResultsFolderPath=TestResults
-            -p:TestCodeCoverage=false
-        ${{ else }}: # x86
-          arguments: >-
-            -t:TestSqlClientUnit
-            -p:TestFramework=${{ parameters.targetFramework }}
-            -p:Configuration=${{ parameters.buildConfiguration }}
-            -p:DotnetPath=${{ parameters.dotnetx86RootPath }}
-            -p:TestFilters="category=flaky"
-            -p:TestResultsFolderPath=TestResults
-            -p:TestCodeCoverage=false
-      continueOnError: true
+  - task: DotNetCoreCLI@2
+    displayName: 'Run Flaky Unit Tests ${{parameters.msbuildArchitecture }}'
+    condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
+    inputs:
+      command: build
+      projects: build.proj
+      ${{ if eq(parameters.msbuildArchitecture, 'x64') }}:
+        arguments: >-
+          -t:TestSqlClientUnit
+          -p:TestFramework=${{ parameters.targetFramework }}
+          -p:ReferenceType=${{ parameters.referenceType }}
+          -p:Configuration=${{ parameters.buildConfiguration }}
+          -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+          -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+          -p:TestFilters="category=flaky"
+          -p:TestResultsFolderPath=TestResults
+          -p:TestCodeCoverage=false
+      ${{ else }}: # x86
+        arguments: >-
+          -t:TestSqlClientUnit
+          -p:TestFramework=${{ parameters.targetFramework }}
+          -p:ReferenceType=${{ parameters.referenceType }}
+          -p:Configuration=${{ parameters.buildConfiguration }}
+          -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+          -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+          -p:DotnetPath=${{ parameters.dotnetx86RootPath }}
+          -p:TestFilters="category=flaky"
+          -p:TestResultsFolderPath=TestResults
+          -p:TestCodeCoverage=false
+    continueOnError: true
 
   - task: DotNetCoreCLI@2
     displayName: 'Run Functional Tests ${{parameters.msbuildArchitecture }}'
@@ -261,33 +272,38 @@ steps:
     continueOnError: true
 
 - ${{ else }}: # Linux or macOS
-  - ${{if eq(parameters.referenceType, 'Project')}}:
-    - task: DotNetCoreCLI@2
-      displayName: 'Run Unit Tests'
-      condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
-      inputs:
-        command: build
-        projects: build.proj
-        arguments: >-
-          -t:TestSqlClientUnit
-          -p:TestFramework=${{ parameters.targetFramework }}
-          -p:Configuration=${{ parameters.buildConfiguration }}
-          -p:TestResultsFolderPath=TestResults
+  - task: DotNetCoreCLI@2
+    displayName: 'Run Unit Tests'
+    condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
+    inputs:
+      command: build
+      projects: build.proj
+      arguments: >-
+        -t:TestSqlClientUnit
+        -p:TestFramework=${{ parameters.targetFramework }}
+        -p:ReferenceType=${{ parameters.referenceType }}
+        -p:Configuration=${{ parameters.buildConfiguration }}
+        -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+        -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+        -p:TestResultsFolderPath=TestResults
 
-    - task: DotNetCoreCLI@2
-      displayName: 'Run Flaky Unit Tests'
-      condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
-      inputs:
-        command: build
-        projects: build.proj
-        arguments: >-
-          -t:TestSqlClientUnit
-          -p:TestFramework=${{ parameters.targetFramework }}
-          -p:Configuration=${{ parameters.buildConfiguration }}
-          -p:TestFilters="category=flaky"
-          -p:TestResultsFolderPath=TestResults
-          -p:TestCodeCoverage=false
-      continueOnError: true
+  - task: DotNetCoreCLI@2
+    displayName: 'Run Flaky Unit Tests'
+    condition: and(eq(variables['setupSucceeded'], 'true'), succeededOrFailed())
+    inputs:
+      command: build
+      projects: build.proj
+      arguments: >-
+        -t:TestSqlClientUnit
+        -p:TestFramework=${{ parameters.targetFramework }}
+        -p:ReferenceType=${{ parameters.referenceType }}
+        -p:Configuration=${{ parameters.buildConfiguration }}
+        -p:PackageVersionSqlClient=${{ parameters.mdsPackageVersion }}
+        -p:PackageVersionSqlServer=${{ parameters.sqlServerPackageVersion }}
+        -p:TestFilters="category=flaky"
+        -p:TestResultsFolderPath=TestResults
+        -p:TestCodeCoverage=false
+    continueOnError: true
 
   - task: DotNetCoreCLI@2
     displayName: 'Run Functional Tests'
diff --git a/src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj b/src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj
index d7a7ef060a..24c6a548f9 100644
--- a/src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj
+++ b/src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj
@@ -62,13 +62,26 @@
 
   <!-- Strong name signing ============================================= -->
   <!-- Strong naming is being done in Directory.Build.props -->
-  <!-- If we're not signing, we are permitted to expose our internals to tests. -->
+
+  <!-- Unsigned: expose internals to UnitTests in any reference mode. -->
   <ItemGroup Condition="'$(SigningKeyPath)' == ''">
     <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
       <_Parameter1>UnitTests</_Parameter1>
     </AssemblyAttribute>
   </ItemGroup>
 
+  <!--
+    Signed + Package mode: expose internals to UnitTests signed with the test key.
+    Signed + Project mode is intentionally omitted: production-signed assemblies should not
+    grant internal access to test assemblies during local development. Tests that need internals
+    in Project mode run unsigned; only the CI package-validation pipeline uses signed packages.
+  -->
+  <ItemGroup Condition="'$(SigningKeyPath)' != '' AND '$(ReferenceType)' == 'Package'">
+    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
+      <_Parameter1>UnitTests, PublicKey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arameter1>
+    </AssemblyAttribute>
+  </ItemGroup>
+
   <!-- Build Output ==================================================== -->
   <PropertyGroup>
     <ArtifactPath>$(RepoRoot)artifacts/</ArtifactPath>
diff --git a/src/Microsoft.Data.SqlClient/tests/Common/Microsoft.Data.SqlClient.TestCommon.csproj b/src/Microsoft.Data.SqlClient/tests/Common/Microsoft.Data.SqlClient.TestCommon.csproj
index 71e4f305e1..548dd641f6 100644
--- a/src/Microsoft.Data.SqlClient/tests/Common/Microsoft.Data.SqlClient.TestCommon.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/Common/Microsoft.Data.SqlClient.TestCommon.csproj
@@ -12,6 +12,13 @@
     <IsTestProject>false</IsTestProject>
   </PropertyGroup>
 
+  <!-- Strong name signing ============================================= -->
+  <!-- Sign with the test key so signed test assemblies can reference this project. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
+
   <!-- Target Frameworks =============================================== -->
   <PropertyGroup>
     <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
@@ -26,7 +33,10 @@
   <!-- References ====================================================== -->
   <!-- Test target reference -->
   <ItemGroup>
-    <ProjectReference Include="$(RepoRoot)src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj" />
+    <ProjectReference Include="$(RepoRoot)src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj"
+                      Condition="'$(ReferenceType)' != 'Package'" />
+    <PackageReference Include="Microsoft.Data.SqlClient"
+                      Condition="'$(ReferenceType)' == 'Package'" />
   </ItemGroup>
 
   <!-- References for netfx -->
diff --git a/src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft.Data.SqlClient.UnitTests.csproj b/src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft.Data.SqlClient.UnitTests.csproj
index 82e900e54c..4501d710a9 100644
--- a/src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft.Data.SqlClient.UnitTests.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft.Data.SqlClient.UnitTests.csproj
@@ -36,22 +36,53 @@
     </None>
   </ItemGroup>
 
+  <!-- Strong name signing ============================================= -->
+  <!-- When a test signing key is provided, sign UnitTests so IVT from signed SqlClient works. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
+
   <!-- References ====================================================== -->
   <!-- Test target reference -->
-  <ItemGroup>
-    <!--
-      The Unit Test project only supports ReferenceType = Project since it needs access to the
-      internals of sibling packages.
-    -->
+  <ItemGroup Condition="'$(ReferenceType)' != 'Package'">
     <ProjectReference Include="$(RepoRoot)src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj" />
     <ProjectReference Include="$(RepoRoot)src/Microsoft.SqlServer.Server/Microsoft.SqlServer.Server.csproj" />
   </ItemGroup>
 
-  <Target Name="ValidateReferenceType"
-          BeforeTargets="Restore;PrepareForBuild"
-          Condition="'$(ReferenceType)' != 'Project'">
-    <Error Text="Microsoft.Data.SqlClient.UnitTests.csproj only supports ReferenceType=Project." />
-  </Target>
+  <!--
+    Package mode: Unit tests exercise internal types that only exist in the implementation assembly
+    (runtimes/{rid}/lib/{tfm}/), not in the ref assembly (ref/{tfm}/).  We exclude the ref
+    compile asset and reference the runtime DLL directly so the compiler can see internals.
+
+    TODO: This is fragile, depending on our SqlClient NuGet package layout and supported TFMs.  It
+    is only necessary because we produce ref and not-supported assemblies and package them.  By
+    default, the compiler will use the ref assemblies if present, which we must explicitly override
+    as explained above.
+  -->
+  <PropertyGroup Condition="'$(ReferenceType)' == 'Package'">
+    <_SqlClientRid Condition="'$(OS)' != 'Windows_NT'">unix</_SqlClientRid>
+    <_SqlClientRid Condition="'$(OS)' == 'Windows_NT'">win</_SqlClientRid>
+    <!-- Map test TFM to the closest available package TFM (package ships net8.0/net9.0/net462) -->
+    <_SqlClientPackageTfm Condition="'$(TargetFramework)' == 'net8.0'">net8.0</_SqlClientPackageTfm>
+    <_SqlClientPackageTfm Condition="'$(TargetFramework)' == 'net462'">net462</_SqlClientPackageTfm>
+    <_SqlClientPackageTfm Condition="'$(_SqlClientPackageTfm)' == ''">net9.0</_SqlClientPackageTfm>
+  </PropertyGroup>
+  <ItemGroup Condition="'$(ReferenceType)' == 'Package'">
+    <!-- Brings in transitive dependencies and runtime deployment; ExcludeAssets="compile" prevents
+         the compiler from using the ref assembly (which only contains public API surface).
+         GeneratePathProperty="true" causes NuGet restore to emit $(PkgMicrosoft_Data_SqlClient)
+         pointing to the extracted package folder in the global packages cache. -->
+    <PackageReference Include="Microsoft.Data.SqlClient"
+                      GeneratePathProperty="true"
+                      ExcludeAssets="compile" />
+    <!-- Compile against the implementation assembly so the compiler can resolve internal types
+         exposed via InternalsVisibleTo.  The path uses $(PkgMicrosoft_Data_SqlClient) generated
+         above to locate the runtime DLL inside the NuGet package layout. -->
+    <Reference Include="Microsoft.Data.SqlClient"
+               HintPath="$(PkgMicrosoft_Data_SqlClient)/runtimes/$(_SqlClientRid)/lib/$(_SqlClientPackageTfm)/Microsoft.Data.SqlClient.dll" />
+    <PackageReference Include="Microsoft.SqlServer.Server" />
+  </ItemGroup>
 
   <!-- References for netframework -->
   <ItemGroup Condition="'$(TargetFramework)' == 'net462'">
diff --git a/src/Microsoft.Data.SqlClient/tests/tools/Microsoft.Data.SqlClient.TestUtilities/Microsoft.Data.SqlClient.TestUtilities.csproj b/src/Microsoft.Data.SqlClient/tests/tools/Microsoft.Data.SqlClient.TestUtilities/Microsoft.Data.SqlClient.TestUtilities.csproj
index 083cca8a61..c50a251e4f 100644
--- a/src/Microsoft.Data.SqlClient/tests/tools/Microsoft.Data.SqlClient.TestUtilities/Microsoft.Data.SqlClient.TestUtilities.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/tools/Microsoft.Data.SqlClient.TestUtilities/Microsoft.Data.SqlClient.TestUtilities.csproj
@@ -2,6 +2,14 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
+
+  <!-- Strong name signing ============================================= -->
+  <!-- Sign with the test key so signed test assemblies can reference this project. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
+
   <Target Name="CopyConfig" BeforeTargets="Compile">
     <Copy SourceFiles="config.default.json" DestinationFiles="config.json" Condition="!Exists('config.json')" />
   </Target>
diff --git a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDS.EndPoint.csproj b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDS.EndPoint.csproj
index 2e1a1b5c81..c9dce97ddb 100644
--- a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDS.EndPoint.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDS.EndPoint.csproj
@@ -3,6 +3,15 @@
     <RootNamespace>Microsoft.SqlServer.TDS.EndPoint</RootNamespace>
     <AssemblyName>Microsoft.SqlServer.TDS.EndPoint</AssemblyName>
     <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+  <!-- Sign when a test key is provided so signed test assemblies can reference this. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
+
+  <PropertyGroup>
     <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TDS.Servers.csproj b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TDS.Servers.csproj
index 57d3dfadd2..b6f33b0977 100644
--- a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TDS.Servers.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TDS.Servers.csproj
@@ -4,6 +4,12 @@
     <AssemblyName>Microsoft.SqlServer.TDS.Servers</AssemblyName>
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
+
+  <!-- Sign when a test key is provided so signed test assemblies can reference this. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="$(RepoRoot)src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDS.EndPoint.csproj" />
     <ProjectReference Include="$(RepoRoot)src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS/TDS.csproj" />
diff --git a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS/TDS.csproj b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS/TDS.csproj
index a4da7c8b92..39d5aae2de 100644
--- a/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS/TDS.csproj
+++ b/src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS/TDS.csproj
@@ -4,4 +4,10 @@
     <AssemblyName>Microsoft.SqlServer.TDS</AssemblyName>
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
+
+  <!-- Sign when a test key is provided so signed test assemblies can reference this. -->
+  <PropertyGroup Condition="'$(TestSigningKeyPath)' != ''">
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(TestSigningKeyPath)</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
 </Project>