diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
index c640e246..90179388 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
@@ -7,6 +7,7 @@
     <ItemGroup>
         <PackageReference Include="Bogus" Version="35.5.1" />
         <PackageReference Include="EvolutionaryArchitecture.Fitnet.Common.Core" Version="4.1.2" />
+        <PackageReference Include="EvolutionaryArchitecture.Fitnet.Common.UnitTesting" Version="4.1.5" />
         <PackageReference Include="FluentAssertions" Version="6.12.0" />
         <PackageReference Include="xunit" Version="2.8.1" />
         <PackageReference Include="xunit.analyzers" Version="1.14.0">
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
index 9ec3ca40..372976d5 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
@@ -1,3 +1,4 @@
 global using ErrorOr;
+global using EvolutionaryArchitecture.Fitnet.Common.UnitTesting.Assertions.ErrorOr;
 global using FluentAssertions;
 global using Xunit;
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
index 91145466..b26a0db1 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
@@ -2,7 +2,7 @@ namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.PrepareContra
 
 using Core.PrepareContract.BusinessRules;
 using Fitnet.Common.Core.BussinessRules;
-using EvolutionaryArchitecture.Fitnet.Common.UnitTesting.Assertions.ErrorOr;
+
 public sealed class ContractCanBePreparedOnlyForAdultRuleTests
 {
     [Fact]