diff --git a/src/embed_tests/Codecs.cs b/src/embed_tests/Codecs.cs
index 6159060b3..f9ea2e14f 100644
--- a/src/embed_tests/Codecs.cs
+++ b/src/embed_tests/Codecs.cs
@@ -25,15 +25,13 @@ static void TupleConversionsGeneric<T, TTuple>()
             TupleCodec<TTuple>.Register();
             var tuple = Activator.CreateInstance(typeof(T), 42, "42", new object());
             T restored = default;
-            using (var scope = Py.CreateScope())
-            {
-                void Accept(T value) => restored = value;
-                using var accept = new Action<T>(Accept).ToPython();
-                scope.Set(nameof(tuple), tuple);
-                scope.Set(nameof(accept), accept);
-                scope.Exec($"{nameof(accept)}({nameof(tuple)})");
-                Assert.That(actual: restored, Is.EqualTo(expected: tuple));
-            }
+            using var scope = Py.CreateScope();
+            void Accept(T value) => restored = value;
+            using var accept = new Action<T>(Accept).ToPython();
+            scope.Set(nameof(tuple), tuple);
+            scope.Set(nameof(accept), accept);
+            scope.Exec($"{nameof(accept)}({nameof(tuple)})");
+            Assert.That(actual: restored, Is.EqualTo(expected: tuple));
         }
 
         [Test]
@@ -46,15 +44,13 @@ static void TupleConversionsObject<T, TTuple>()
             TupleCodec<TTuple>.Register();
             var tuple = Activator.CreateInstance(typeof(T), 42.0, "42", new object());
             T restored = default;
-            using (var scope = Py.CreateScope())
-            {
-                void Accept(object value) => restored = (T)value;
-                using var accept = new Action<object>(Accept).ToPython();
-                scope.Set(nameof(tuple), tuple);
-                scope.Set(nameof(accept), accept);
-                scope.Exec($"{nameof(accept)}({nameof(tuple)})");
-                Assert.That(actual: restored, Is.EqualTo(expected: tuple));
-            }
+            using var scope = Py.CreateScope();
+            void Accept(object value) => restored = (T)value;
+            using var accept = new Action<object>(Accept).ToPython();
+            scope.Set(nameof(tuple), tuple);
+            scope.Set(nameof(accept), accept);
+            scope.Exec($"{nameof(accept)}({nameof(tuple)})");
+            Assert.That(actual: restored, Is.EqualTo(expected: tuple));
         }
 
         [Test]
@@ -92,7 +88,7 @@ public void ListDecoderTest()
             var codec = ListDecoder.Instance;
             var items = new List<PyObject>() { new PyInt(1), new PyInt(2), new PyInt(3) };
 
-            using var pyList = new PyList(items.ToArray());
+            using var pyList = new PyList([.. items]);
 
             using var pyListType = pyList.GetPythonType();
             Assert.IsTrue(codec.CanDecode(pyListType, typeof(IList<bool>)));
@@ -119,7 +115,7 @@ public void ListDecoderTest()
             IList<string> stringList = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyList, out stringList); });
             Assert.That(3, Is.EqualTo(stringList.Count));
-            Assert.Throws(typeof(InvalidCastException), () => { var x = stringList[0]; });
+            Assert.Throws<InvalidCastException>(() => { var x = stringList[0]; });
 
             //can't convert python iterable to list (this will require a copy which isn't lossless)
             using var foo = GetPythonIterable();
@@ -134,7 +130,7 @@ public void SequenceDecoderTest()
             var items = new List<PyObject>() { new PyInt(1), new PyInt(2), new PyInt(3) };
 
             //SequenceConverter can only convert to any ICollection
-            using var pyList = new PyList(items.ToArray());
+            using var pyList = new PyList([.. items]);
             using var listType = pyList.GetPythonType();
             //it can convert a PyList, since PyList satisfies the python sequence protocol
 
@@ -162,7 +158,7 @@ public void SequenceDecoderTest()
             //the IList will report a Count of 3.
             ICollection<string> stringCollection = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyList, out stringCollection); });
-            Assert.That(stringCollection.Count(), Is.EqualTo(3));
+            Assert.That(stringCollection.Count, Is.EqualTo(3));
             Assert.Throws<InvalidCastException>(() => {
                 string[] array = new string[3];
                 stringCollection.CopyTo(array, 0);
@@ -177,7 +173,7 @@ public void SequenceDecoderTest()
             Assert.IsFalse(codec.CanDecode(fooType, typeof(ICollection<int>)));
 
             //python tuples do satisfy the python sequence protocol
-            var pyTuple = new PyTuple(items.ToArray());
+            var pyTuple = new PyTuple([.. items]);
             var pyTupleType = pyTuple.GetPythonType();
 
             Assert.IsTrue(codec.CanDecode(pyTupleType, typeof(ICollection<float>)));
@@ -215,7 +211,7 @@ public void IterableDecoderTest()
             var codec = IterableDecoder.Instance;
             var items = new List<PyObject>() { new PyInt(1), new PyInt(2), new PyInt(3) };
 
-            var pyList = new PyList(items.ToArray());
+            var pyList = new PyList([.. items]);
             var pyListType = pyList.GetPythonType();
             Assert.IsFalse(codec.CanDecode(pyListType, typeof(IList<bool>)));
             Assert.IsTrue(codec.CanDecode(pyListType, typeof(System.Collections.IEnumerable)));
@@ -249,13 +245,13 @@ public void IterableDecoderTest()
             IEnumerable<string> stringEnumerable = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyList, out stringEnumerable); });
 
-            Assert.Throws(typeof(InvalidCastException), () => {
+            Assert.Throws<InvalidCastException>(() => {
                 foreach (string item in stringEnumerable)
                 {
                     var x = item;
                 }
             });
-            Assert.Throws(typeof(InvalidCastException), () => {
+            Assert.Throws<InvalidCastException>(() => {
                 stringEnumerable.Count();
             });
 
@@ -309,7 +305,7 @@ def CanEncode(self, clr_type):
         public void ExceptionEncoded()
         {
             PyObjectConversions.RegisterEncoder(new ValueErrorCodec());
-            void CallMe() => throw new ValueErrorWrapper(TestExceptionMessage);
+            static void CallMe() => throw new ValueErrorWrapper(TestExceptionMessage);
             var callMeAction = new Action(CallMe);
             using var scope = Py.CreateScope();
             scope.Exec(@"
@@ -385,7 +381,9 @@ public void ExceptionDecodedNoInstance()
             }
         }
 
+#pragma warning disable IDE0060 // Remove unused parameter
         public static void AcceptsDateTime(DateTime v) {}
+#pragma warning restore IDE0060 // Remove unused parameter
 
         [Test]
         public void As_Object_AffectedByDecoders()
@@ -412,15 +410,14 @@ public bool TryDecode<T>(PyObject pyObj, out T value)
             }
         }
 
-        class ValueErrorWrapper : Exception
+        class ValueErrorWrapper(string message) : Exception(message)
         {
-            public ValueErrorWrapper(string message) : base(message) { }
         }
 
         class ValueErrorCodec : IPyObjectEncoder, IPyObjectDecoder
         {
             public bool CanDecode(PyType objectType, Type targetType)
-                => this.CanEncode(targetType)
+                => CanEncode(targetType)
                    && PythonReferenceComparer.Instance.Equals(objectType, PythonEngine.Eval("ValueError"));
 
             public bool CanEncode(Type type) => type == typeof(ValueErrorWrapper)
@@ -480,16 +477,10 @@ class ObjectToEncoderInstanceEncoder<T> : IPyObjectEncoder
     /// Decodes object of specified Python type to the predefined value <see cref="DecodeResult"/>
     /// </summary>
     /// <typeparam name="TTarget">Type of the <see cref="DecodeResult"/></typeparam>
-    class DecoderReturningPredefinedValue<TTarget> : IPyObjectDecoder
+    class DecoderReturningPredefinedValue<TTarget>(PyObject objectType, TTarget decodeResult) : IPyObjectDecoder
     {
-        public PyObject TheOnlySupportedSourceType { get; }
-        public TTarget DecodeResult { get; }
-
-        public DecoderReturningPredefinedValue(PyObject objectType, TTarget decodeResult)
-        {
-            this.TheOnlySupportedSourceType = objectType;
-            this.DecodeResult = decodeResult;
-        }
+        public PyObject TheOnlySupportedSourceType { get; } = objectType;
+        public TTarget DecodeResult { get; } = decodeResult;
 
         public bool CanDecode(PyType objectType, Type targetType)
             => PythonReferenceComparer.Instance.Equals(objectType, TheOnlySupportedSourceType)
@@ -497,7 +488,7 @@ public bool CanDecode(PyType objectType, Type targetType)
         public bool TryDecode<T>(PyObject pyObj, out T value)
         {
             if (typeof(T) != typeof(TTarget))
-                throw new ArgumentException(nameof(T));
+                throw new ArgumentException(null, nameof(T));
             value = (T)(object)DecodeResult;
             return true;
         }
diff --git a/src/embed_tests/Dynamic.cs b/src/embed_tests/Dynamic.cs
index 9d35bfacc..b5b13f1a7 100644
--- a/src/embed_tests/Dynamic.cs
+++ b/src/embed_tests/Dynamic.cs
@@ -35,10 +35,10 @@ public void AssignNone()
         {
             dynamic sys = Py.Import("sys");
             sys.testattr = new StringBuilder();
-            Assert.IsNotNull(sys.testattr);
+            Assert.That(sys.testattr, Is.Not.Null);
 
             sys.testattr = null;
-            Assert.IsNull(sys.testattr);
+            Assert.That(sys.testattr, Is.Null);
         }
 
         /// <summary>
@@ -80,7 +80,7 @@ public void PassObjectInPython()
             Assert.That(sys.testattr3.ToString(), Is.EqualTo("True"));
 
             // Compare in .NET
-            Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));
+            Assert.That(sys.testattr1, Is.EqualTo(sys.testattr2));
         }
 
         /// <summary>
@@ -103,7 +103,7 @@ public void PassPyObjectInNet()
             Assert.That(sys.testattr3.ToString(), Is.EqualTo("True"));
 
             // Compare in .NET
-            Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));
+            Assert.That(sys.testattr1, Is.EqualTo(sys.testattr2));
         }
 
         // regression test for https://github.com/pythonnet/pythonnet/issues/1848
@@ -119,13 +119,13 @@ class MyEnum(enum.IntEnum):
     ERROR = 2
 
 def get_status():
-    return MyEnum.OK 
+    return MyEnum.OK
 "
 );
 
             dynamic MyEnum = scope.Get("MyEnum");
             dynamic status = scope.Get("get_status").Invoke();
-            Assert.IsTrue(status == MyEnum.OK);
+            Assert.That(status, Is.EqualTo(MyEnum.OK));
         }
 
         // regression test for https://github.com/pythonnet/pythonnet/issues/1680
diff --git a/src/embed_tests/NumPyTests.cs b/src/embed_tests/NumPyTests.cs
index 57ff11b2b..4bd7356d7 100644
--- a/src/embed_tests/NumPyTests.cs
+++ b/src/embed_tests/NumPyTests.cs
@@ -67,12 +67,12 @@ public void VarArg()
         {
             dynamic zX = np.array(new[,] { { 1, 2, 3 }, { 4, 5, 6 }, { 8, 9, 0 } });
             dynamic grad = np.gradient(zX, 4.0, 5.0);
-            dynamic grad2 = np.InvokeMethod("gradient", new PyObject[] {zX, new PyFloat(4.0), new PyFloat(5.0)});
+            dynamic grad2 = np.InvokeMethod("gradient", new PyObject[] { zX, new PyFloat(4.0), new PyFloat(5.0) });
 
-            Assert.AreEqual(4.125, grad[0].sum().__float__().As<double>(), 0.001);
-            Assert.AreEqual(-1.2, grad[1].sum().__float__().As<double>(), 0.001);
-            Assert.AreEqual(4.125, grad2[0].sum().__float__().As<double>(), 0.001);
-            Assert.AreEqual(-1.2, grad2[1].sum().__float__().As<double>(), 0.001);
+            Assert.That(grad[0].sum().__float__().As<double>(), Is.EqualTo(4.125).Within(0.001));
+            Assert.That(grad[1].sum().__float__().As<double>(), Is.EqualTo(-1.2).Within(0.001));
+            Assert.That(grad2[0].sum().__float__().As<double>(), Is.EqualTo(4.125).Within(0.001));
+            Assert.That(grad2[1].sum().__float__().As<double>(), Is.EqualTo(-1.2).Within(0.001));
         }
 
 #pragma warning disable IDE1006
diff --git a/src/embed_tests/Python.EmbeddingTest.csproj b/src/embed_tests/Python.EmbeddingTest.csproj
index 15258fc83..8697e7aaf 100644
--- a/src/embed_tests/Python.EmbeddingTest.csproj
+++ b/src/embed_tests/Python.EmbeddingTest.csproj
@@ -24,7 +24,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="NUnit" Version="3.*" />
+    <PackageReference Include="NUnit" Version="5.*" />
     <!-- PackageReference Include="NUnit.Analyzers" Version="4.10.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
diff --git a/src/embed_tests/TestFinalizer.cs b/src/embed_tests/TestFinalizer.cs
index d6a3c39e9..47e18277d 100644
--- a/src/embed_tests/TestFinalizer.cs
+++ b/src/embed_tests/TestFinalizer.cs
@@ -67,7 +67,8 @@ public void CollectBasicObject()
 
             Warn.If(shortWeak.IsAlive,
                 "shortWeak is alive after FullGCCollect; runtime hasn't reclaimed the wrapper yet",
-                shortWeak);
+                shortWeak.ToString()
+            );
             // longWeak.IsAlive at this point is .NET-GC-implementation-defined
             // (Framework reclaims post-finalize objects more eagerly than Core);
             // intentionally not asserted.
diff --git a/src/python_tests_runner/Python.PythonTestsRunner.csproj b/src/python_tests_runner/Python.PythonTestsRunner.csproj
index 9f782bd2b..bf9c67f66 100644
--- a/src/python_tests_runner/Python.PythonTestsRunner.csproj
+++ b/src/python_tests_runner/Python.PythonTestsRunner.csproj
@@ -10,7 +10,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="NUnit" Version="4.*" />
+    <PackageReference Include="NUnit" Version="5.*" />
     <PackageReference Include="NUnit3TestAdapter" Version="6.*">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>