diff --git a/src/Testcontainers/Builders/BuildConfiguration.cs b/src/Testcontainers/Builders/BuildConfiguration.cs
index 408fad9b3..b96a71c48 100644
--- a/src/Testcontainers/Builders/BuildConfiguration.cs
+++ b/src/Testcontainers/Builders/BuildConfiguration.cs
@@ -16,7 +16,7 @@ public static class BuildConfiguration
     /// <returns>Changed configuration object. If there is no change, the previous configuration object.</returns>
     public static T Combine<T>(T oldValue, T newValue)
     {
-      return newValue == null ? oldValue : newValue;
+      return Equals(default(T), newValue) ? oldValue : newValue;
     }
 
     /// <summary>
diff --git a/src/Testcontainers/Guard.Argument.cs b/src/Testcontainers/Guard.Argument.cs
index 8059f3ab5..d0189c5e5 100644
--- a/src/Testcontainers/Guard.Argument.cs
+++ b/src/Testcontainers/Guard.Argument.cs
@@ -56,7 +56,7 @@ public ArgumentInfo(TType value, string name)
       /// <returns>True if the argument has a value; otherwise, false.</returns>
       public bool HasValue()
       {
-        return Value != null;
+        return !Equals(default(TType), Value);
       }
     }
   }
diff --git a/src/Testcontainers/Images/DockerImage.cs b/src/Testcontainers/Images/DockerImage.cs
index 671211af2..b37ae0c4a 100644
--- a/src/Testcontainers/Images/DockerImage.cs
+++ b/src/Testcontainers/Images/DockerImage.cs
@@ -14,6 +14,8 @@ public sealed class DockerImage : IImage
 
     private static readonly char[] TrimChars = { ' ', ':', '/' };
 
+    private static readonly char[] HostnameIdentifierChars = { '.', ':' };
+
     private readonly string _hubImageNamePrefix;
 
     private readonly Lazy<string> _lazyFullName;
@@ -86,14 +88,7 @@ public DockerImage(
           .First()
           .Split('/')[0];
 
-        if (firstSegmentOfRepository.IndexOfAny(new[] { '.', ':' }) >= 0)
-        {
-          return firstSegmentOfRepository;
-        }
-        else
-        {
-          return null;
-        }
+        return firstSegmentOfRepository.IndexOfAny(HostnameIdentifierChars) >= 0 ? firstSegmentOfRepository : null;
       });
     }
 
diff --git a/src/Testcontainers/Images/DockerfileArchive.cs b/src/Testcontainers/Images/DockerfileArchive.cs
index c752ca050..c543e17f8 100644
--- a/src/Testcontainers/Images/DockerfileArchive.cs
+++ b/src/Testcontainers/Images/DockerfileArchive.cs
@@ -55,7 +55,7 @@ public DockerfileArchive(DirectoryInfo dockerfileDirectory, FileInfo dockerfile,
         throw new ArgumentException($"Directory '{dockerfileDirectory.FullName}' does not exist.");
       }
 
-      if (!dockerfileDirectory.GetFiles(dockerfile.ToString(), SearchOption.TopDirectoryOnly).Any())
+      if (dockerfileDirectory.GetFiles(dockerfile.ToString(), SearchOption.TopDirectoryOnly).Length == 0)
       {
         throw new ArgumentException($"{dockerfile} does not exist in '{dockerfileDirectory.FullName}'.");
       }
diff --git a/tests/Testcontainers.Commons/CommonImages.cs b/tests/Testcontainers.Commons/CommonImages.cs
index 4e0416655..84e1090e2 100644
--- a/tests/Testcontainers.Commons/CommonImages.cs
+++ b/tests/Testcontainers.Commons/CommonImages.cs
@@ -3,7 +3,7 @@ namespace DotNet.Testcontainers.Commons;
 [PublicAPI]
 public static class CommonImages
 {
-    public static readonly IImage Ryuk = new DockerImage("testcontainers/ryuk:0.5.1");
+    public static readonly IImage Ryuk = new DockerImage("testcontainers/ryuk:0.6.0");
 
     public static readonly IImage Alpine = new DockerImage("alpine:3.17");
 
diff --git a/tests/Testcontainers.Databases.Tests/DatabasesContainerTest.cs b/tests/Testcontainers.Databases.Tests/DatabasesContainerTest.cs
index 694f7b5ec..5aff13fd4 100644
--- a/tests/Testcontainers.Databases.Tests/DatabasesContainerTest.cs
+++ b/tests/Testcontainers.Databases.Tests/DatabasesContainerTest.cs
@@ -16,8 +16,10 @@ public void ShouldNotImplementIDatabaseContainer(Type type)
         Assert.False(type.IsAssignableTo(typeof(IDatabaseContainer)), $"The type '{type.Name}' does implement the database interface.");
     }
 
-    public static IEnumerable<object[]> GetContainerImplementations(bool expectDataProvider)
+    public static TheoryData<Type> GetContainerImplementations(bool expectDataProvider)
     {
+        var theoryData = new TheoryData<Type>();
+
         var testAssemblies = Directory.GetFiles(".", "Testcontainers.*.Tests.dll", SearchOption.TopDirectoryOnly)
             .Select(Path.GetFullPath)
             .Select(Assembly.LoadFrom)
@@ -41,14 +43,16 @@ public static IEnumerable<object[]> GetContainerImplementations(bool expectDataP
 
                 if (expectDataProvider && hasDataProvider)
                 {
-                    yield return new object[] { containerType };
+                    theoryData.Add(containerType);
                 }
 
                 if (!expectDataProvider && !hasDataProvider)
                 {
-                    yield return new object[] { containerType };
+                    theoryData.Add(containerType);
                 }
             }
         }
+
+        return theoryData;
     }
 }
\ No newline at end of file
diff --git a/tests/Testcontainers.Tests/Unit/Configurations/DockerImageNameSubstitutionTest.cs b/tests/Testcontainers.Tests/Unit/Configurations/DockerImageNameSubstitutionTest.cs
index 69ca5f76d..e316dfb55 100644
--- a/tests/Testcontainers.Tests/Unit/Configurations/DockerImageNameSubstitutionTest.cs
+++ b/tests/Testcontainers.Tests/Unit/Configurations/DockerImageNameSubstitutionTest.cs
@@ -1,7 +1,6 @@
 namespace DotNet.Testcontainers.Tests.Unit
 {
   using System;
-  using System.Collections.Generic;
   using DotNet.Testcontainers.Builders;
   using DotNet.Testcontainers.Configurations;
   using DotNet.Testcontainers.Containers;
@@ -14,20 +13,20 @@ public static class DockerImageNameSubstitutionTest
     [Collection(nameof(DockerImageNameSubstitutionTest))]
     public sealed class HubImageNamePrefixIsSet : IDisposable
     {
-      public static IEnumerable<object[]> Substitutions { get; }
-        = new[]
+      public static TheoryData<string, string, string> Substitutions { get; }
+        = new TheoryData<string, string, string>
         {
-          new[] { "my.proxy.com", "bar", "my.proxy.com/bar:latest" },
-          new[] { "my.proxy.com", "bar:latest", "my.proxy.com/bar:latest" },
-          new[] { "my.proxy.com", "bar:1.0.0", "my.proxy.com/bar:1.0.0" },
-          new[] { "my.proxy.com/my-path", "bar:1.0.0", "my.proxy.com/my-path/bar:1.0.0" },
-          new[] { "my.proxy.com:443", "bar:1.0.0", "my.proxy.com:443/bar:1.0.0" },
-          new[] { "my.proxy.com", "foo/bar:1.0.0", "my.proxy.com/foo/bar:1.0.0" },
-          new[] { "my.proxy.com/my-path", "foo/bar:1.0.0", "my.proxy.com/my-path/foo/bar:1.0.0" },
-          new[] { "my.proxy.com:443", "foo/bar:1.0.0", "my.proxy.com:443/foo/bar:1.0.0" },
-          new[] { "my.proxy.com:443/my-path", "foo/bar:1.0.0", "my.proxy.com:443/my-path/foo/bar:1.0.0" },
-          new[] { "my.proxy.com", "myregistry.azurecr.io/foo/bar:1.0.0", "myregistry.azurecr.io/foo/bar:1.0.0" },
-          new[] { "my.proxy.com", "myregistry.azurecr.io:443/foo/bar:1.0.0", "myregistry.azurecr.io:443/foo/bar:1.0.0" },
+          { "my.proxy.com", "bar", "my.proxy.com/bar:latest" },
+          { "my.proxy.com", "bar:latest", "my.proxy.com/bar:latest" },
+          { "my.proxy.com", "bar:1.0.0", "my.proxy.com/bar:1.0.0" },
+          { "my.proxy.com/my-path", "bar:1.0.0", "my.proxy.com/my-path/bar:1.0.0" },
+          { "my.proxy.com:443", "bar:1.0.0", "my.proxy.com:443/bar:1.0.0" },
+          { "my.proxy.com", "foo/bar:1.0.0", "my.proxy.com/foo/bar:1.0.0" },
+          { "my.proxy.com/my-path", "foo/bar:1.0.0", "my.proxy.com/my-path/foo/bar:1.0.0" },
+          { "my.proxy.com:443", "foo/bar:1.0.0", "my.proxy.com:443/foo/bar:1.0.0" },
+          { "my.proxy.com:443/my-path", "foo/bar:1.0.0", "my.proxy.com:443/my-path/foo/bar:1.0.0" },
+          { "my.proxy.com", "myregistry.azurecr.io/foo/bar:1.0.0", "myregistry.azurecr.io/foo/bar:1.0.0" },
+          { "my.proxy.com", "myregistry.azurecr.io:443/foo/bar:1.0.0", "myregistry.azurecr.io:443/foo/bar:1.0.0" },
         };
 
       [Theory]