diff --git a/.github/workflows/cmake-multi-platform.yml b/.github/workflows/cmake-multi-platform.yml
index e995f98..6ccea9b 100644
--- a/.github/workflows/cmake-multi-platform.yml
+++ b/.github/workflows/cmake-multi-platform.yml
@@ -1,6 +1,6 @@
 # This starter workflow is for a CMake project running on multiple platforms. There is a different starter workflow if you just want a single platform.
 # See: https://github.com/actions/starter-workflows/blob/main/ci/cmake-single-platform.yml
-name: CMake on multiple platforms
+name: Multi-platform Build and Test
 
 on:
   push:
diff --git a/include/mioc/detail/ServiceContainer.h b/include/mioc/detail/ServiceContainer.h
index dfc7460..8059632 100644
--- a/include/mioc/detail/ServiceContainer.h
+++ b/include/mioc/detail/ServiceContainer.h
@@ -26,10 +26,10 @@ class ServiceContainer final
     }
 
     // Any copy of service container is not allowed.
-    ServiceContainer(const ServiceContainer&) = delete;
-    ServiceContainer(const ServiceContainer&&) = delete;
-    ServiceContainer& operator=(const ServiceContainer&) = delete;
-    ServiceContainer& operator=(const ServiceContainer&&) = delete;
+    ServiceContainer(const ServiceContainer& other) = default;
+    ServiceContainer& operator=(const ServiceContainer& other) = default;
+    ServiceContainer(ServiceContainer&& other) noexcept = default;
+    ServiceContainer& operator=(ServiceContainer&& other) noexcept = default;
 
     ~ServiceContainer() = default;
 
diff --git a/include/mioc/detail/SingletonContainer.h b/include/mioc/detail/SingletonContainer.h
index 3738e13..1ab51e4 100644
--- a/include/mioc/detail/SingletonContainer.h
+++ b/include/mioc/detail/SingletonContainer.h
@@ -28,9 +28,6 @@ class SingletonContainer final
 private:
     // Prevent instantiation.
     SingletonContainer() = default;
-
-    static std::shared_ptr<ServiceContainer> _container;
-    static bool _lazy;
 };
 
 MIOC_END
diff --git a/src/ServiceContainer.cpp b/src/ServiceContainer.cpp
index a843209..4ae8d5f 100644
--- a/src/ServiceContainer.cpp
+++ b/src/ServiceContainer.cpp
@@ -2,6 +2,8 @@
 
 #include <mioc/detail/ServiceContainer.h>
 
+#include <utility>
+
 MIOC_BEGIN
 
 // This is a random number, change it as you wish.
diff --git a/src/SingletonContainer.cpp b/src/SingletonContainer.cpp
index 9037997..fb23c02 100644
--- a/src/SingletonContainer.cpp
+++ b/src/SingletonContainer.cpp
@@ -6,20 +6,13 @@ MIOC_BEGIN
 
 ServiceContainerPtr SingletonContainer::GetContainer()
 {
-    if (_container == nullptr)
-    {
-        _container = ServiceContainer::New(_lazy);
-    }
-    return _container;
+    return GetContainer(DEFAULT_LAZINESS);
 }
 
 ServiceContainerPtr SingletonContainer::GetContainer(bool lazy)
 {
-    _lazy = lazy;
-    return GetContainer();
+    static std::shared_ptr<ServiceContainer> container = ServiceContainer::New(lazy);
+    return container;
 }
 
-std::shared_ptr<ServiceContainer> SingletonContainer::_container;
-bool SingletonContainer::_lazy = DEFAULT_LAZINESS;
-
 MIOC_END
diff --git a/tests/AssignmentTest.cpp b/tests/AssignmentTest.cpp
new file mode 100644
index 0000000..ebfae91
--- /dev/null
+++ b/tests/AssignmentTest.cpp
@@ -0,0 +1,37 @@
+#include <mioc/mioc.h>
+#include "Test.h"
+#include "doctest.h"
+
+TEST_CASE("Assignment")
+{
+    mioc::ServiceContainerPtr containerA = mioc::ServiceContainer::New();
+    mioc::ServiceContainerPtr containerB = mioc::ServiceContainer::New();
+
+    // Register interfaces and implementations.
+    containerA->AddSingleton<IA, A>();
+    containerA->AddSingleton<IB, B, IA>();
+
+    // Copy container.
+    *containerB = *containerA;
+
+    auto a1 = containerA->Resolve<IA>();
+    auto a2 = containerB->Resolve<IA>();
+    CHECK_EQ(a1->ToString(), a2->ToString());
+
+    const auto b1 = containerA->Resolve<IB>();
+    const auto b2 = containerB->Resolve<IB>();
+    CHECK_EQ(b1->ToString(), b2->ToString());
+
+    // Register new instance.
+    const std::shared_ptr<IC> c = std::make_shared<C>(b1);
+    containerA->AddSingleton(c);
+    CHECK_NE(containerA->Resolve<IC>(), nullptr);
+    CHECK_EQ(containerB->Resolve<IC>(), nullptr);
+
+    // Move container.
+    mioc::ServiceContainerPtr containerC = mioc::ServiceContainer::New();
+    *containerC = std::move(*containerA);
+    CHECK_EQ(containerC->Resolve<IA>()->ToString(), a1->ToString());
+    CHECK_EQ(containerC->Resolve<IB>()->ToString(), b1->ToString());
+    CHECK_EQ(containerC->Resolve<IC>(), nullptr);
+}
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 8839cd0..2eb18a0 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -1,8 +1,9 @@
-aux_source_directory(. TEST_FILES)
-add_executable(tests ${TEST_FILES})
+set(LIBRARIES mioc)
+set(MIOC_TESTS SingletonTest TransientTest AssignmentTest)
 
-target_include_directories(tests PRIVATE .)
-
-target_link_libraries(tests mioc)
-
-add_test(NAME TestAll COMMAND tests)
+foreach(test ${MIOC_TESTS})
+    add_executable(${test} doctest.cpp ${test}.cpp)
+    target_include_directories(${test} PRIVATE .)
+    target_link_libraries(${test} ${LIBRARIES})
+    add_test(NAME ${test} COMMAND ${test})
+endforeach(test ${MIOC_TESTS})
diff --git a/tests/Transient.cpp b/tests/TransientTest.cpp
similarity index 100%
rename from tests/Transient.cpp
rename to tests/TransientTest.cpp