Give a strong name for the assembly.

Assemblies are signed with keys without password.

DocX/DocX.csproj

     <DebugSymbols>true</DebugSymbols>
   </PropertyGroup>
   <PropertyGroup>
-    <SignAssembly>false</SignAssembly>
+    <SignAssembly>true</SignAssembly>
   </PropertyGroup>
   <PropertyGroup>
-    <AssemblyOriginatorKeyFile>
-    </AssemblyOriginatorKeyFile>
+    <AssemblyOriginatorKeyFile>KeyWithoutPassword.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
     <EmbeddedResource Include="Resources\numbering.default_bullet_abstract.xml.gz" />
     <EmbeddedResource Include="Resources\numbering.default_decimal_abstract.xml.gz" />
   </ItemGroup>
+  <ItemGroup>
+    <None Include="KeyWithoutPassword.snk" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

DocX/Properties/AssemblyInfo.cs

 [assembly: AssemblyCulture("")]
 
 // Allow the UnitTests to get at internal stuff.
-[assembly: InternalsVisibleTo("UnitTests")]
+[assembly: InternalsVisibleTo( "UnitTests, PublicKey=" +
+"0024000004800000940000000602000000240000525341310004000001000100b739555cdacfd1" +
+"f59b61e7fb189ed886849ae10d0f8a876cd700d36286addf1d4a6854bb23b12fad5700b64787e9" +
+"9b0b9f0ed0d64d86d591a32e58080470bdc9a61845301edf6cbb447c3578718763d3f93694a2ac" +
+"fdac1c2d096343f3d7085ea1c20fcfeb1d8bac4153204c9faa40c29be2dc38056116e756ff7bbf" +
+"9d82e3ab" )]
 
 // Setting ComVisible to false makes the types in this assembly not visible 
 // to COM components.  If you need to access a type in this assembly from 

UnitTests/UnitTests.csproj

     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
   <PropertyGroup>
-    <SignAssembly>false</SignAssembly>
+    <SignAssembly>true</SignAssembly>
   </PropertyGroup>
   <PropertyGroup>
-    <AssemblyOriginatorKeyFile>
-    </AssemblyOriginatorKeyFile>
+    <AssemblyOriginatorKeyFile>KeyWithoutPassword.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="nunit.framework, Version=3.6.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb, processorArchitecture=MSIL">
     <None Include="documents\VariousTextFormatting.docx">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Include="KeyWithoutPassword.snk" />
     <None Include="packages.config">
       <SubType>Designer</SubType>
     </None>