pythonnet · filmor · May 12, 2026 · May 12, 2026 · May 12, 2026
diff --git a/Directory.Build.props b/Directory.Build.props
@@ -4,7 +4,7 @@
     <AssemblyCopyright>Copyright (c) 2006-2025 The Contributors of the Python.NET Project</AssemblyCopyright>
     <AssemblyCompany>pythonnet</AssemblyCompany>
     <AssemblyProduct>Python.NET</AssemblyProduct>
-    <LangVersion>12.0</LangVersion>
+    <LangVersion>14</LangVersion>
     <IsPackable>false</IsPackable>
     <DeterministicSourcePaths>true</DeterministicSourcePaths>
     <FullVersion>$([System.IO.File]::ReadAllText("$(MSBuildThisFileDirectory)version.txt").Trim())</FullVersion>

diff --git a/src/embed_tests/Codecs.cs b/src/embed_tests/Codecs.cs
@@ -32,7 +32,7 @@ static void TupleConversionsGeneric<T, TTuple>()
                 scope.Set(nameof(tuple), tuple);
                 scope.Set(nameof(accept), accept);
                 scope.Exec($"{nameof(accept)}({nameof(tuple)})");
-                Assert.AreEqual(expected: tuple, actual: restored);
+                Assert.That(actual: restored, Is.EqualTo(expected: tuple));
             }
         }
 
@@ -53,7 +53,7 @@ static void TupleConversionsObject<T, TTuple>()
                 scope.Set(nameof(tuple), tuple);
                 scope.Set(nameof(accept), accept);
                 scope.Exec($"{nameof(accept)}({nameof(tuple)})");
-                Assert.AreEqual(expected: tuple, actual: restored);
+                Assert.That(actual: restored, Is.EqualTo(expected: tuple));
             }
         }
 
@@ -67,7 +67,7 @@ static void TupleRoundtripObject<T, TTuple>()
             var tuple = Activator.CreateInstance(typeof(T), 42.0, "42", new object());
             using var pyTuple = TupleCodec<TTuple>.Instance.TryEncode(tuple);
             Assert.IsTrue(TupleCodec<TTuple>.Instance.TryDecode(pyTuple, out object restored));
-            Assert.AreEqual(expected: tuple, actual: restored);
+            Assert.That(actual: restored, Is.EqualTo(expected: tuple));
         }
 
         [Test]
@@ -81,7 +81,7 @@ static void TupleRoundtripGeneric<T, TTuple>()
             var tuple = Activator.CreateInstance(typeof(T), 42, "42", new object());
             using var pyTuple = TupleCodec<TTuple>.Instance.TryEncode(tuple);
             Assert.IsTrue(TupleCodec<TTuple>.Instance.TryDecode(pyTuple, out T restored));
-            Assert.AreEqual(expected: tuple, actual: restored);
+            Assert.That(actual: restored, Is.EqualTo(expected: tuple));
         }
 
         static PyObject GetPythonIterable() => PythonEngine.Eval("map(lambda x: x, [1,2,3])");
@@ -118,7 +118,7 @@ public void ListDecoderTest()
             //the IList will report a Count of 3.
             IList<string> stringList = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyList, out stringList); });
-            Assert.AreEqual(stringList.Count, 3);
+            Assert.That(3, Is.EqualTo(stringList.Count));
             Assert.Throws(typeof(InvalidCastException), () => { var x = stringList[0]; });
 
             //can't convert python iterable to list (this will require a copy which isn't lossless)
@@ -162,8 +162,8 @@ public void SequenceDecoderTest()
             //the IList will report a Count of 3.
             ICollection<string> stringCollection = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyList, out stringCollection); });
-            Assert.AreEqual(3, stringCollection.Count());
-            Assert.Throws(typeof(InvalidCastException), () => {
+            Assert.That(stringCollection.Count(), Is.EqualTo(3));
+            Assert.Throws<InvalidCastException>(() => {
                 string[] array = new string[3];
                 stringCollection.CopyTo(array, 0);
             });
@@ -199,8 +199,8 @@ public void SequenceDecoderTest()
             //the IList will report a Count of 3.
             ICollection<string> stringCollection2 = null;
             Assert.DoesNotThrow(() => { codec.TryDecode(pyTuple, out stringCollection2); });
-            Assert.AreEqual(3, stringCollection2.Count());
-            Assert.Throws(typeof(InvalidCastException), () => {
+            Assert.That(stringCollection2.Count, Is.EqualTo(3));
+            Assert.Throws<InvalidCastException>(() => {
                 string[] array = new string[3];
                 stringCollection2.CopyTo(array, 0);
             });
@@ -321,7 +321,7 @@ def call(func):
 ");
             var callFunc = scope.Get("call");
             string message = callFunc.Invoke(callMeAction.ToPython()).As<string>();
-            Assert.AreEqual(TestExceptionMessage, message);
+            Assert.That(message, Is.EqualTo(TestExceptionMessage));
         }
 
         [Test]
@@ -331,7 +331,7 @@ public void ExceptionDecoded()
             using var scope = Py.CreateScope();
             var error = Assert.Throws<ValueErrorWrapper>(()
                 => PythonEngine.Exec($"raise ValueError('{TestExceptionMessage}')"));
-            Assert.AreEqual(TestExceptionMessage, error.Message);
+            Assert.That(error.Message, Is.EqualTo(TestExceptionMessage));
         }
 
         [Test]
@@ -360,7 +360,7 @@ public void FloatDerivedDecoded()
             PyObjectConversions.RegisterDecoder(decoder);
             using var result = scope.Eval("FloatDerived()");
             object decoded = result.As<object>();
-            Assert.AreEqual(42, decoded);
+            Assert.That(decoded, Is.EqualTo(42));
         }
 
         [Test]
@@ -374,7 +374,7 @@ public void ExceptionDecodedNoInstance()
                 var error = Assert.Throws<ValueErrorWrapper>(() =>
                     PythonEngine.Exec($"[].__iter__().__next__()")
                 );
-                Assert.AreEqual(TestExceptionMessage, error.Message);
+                Assert.That(error.Message, Is.EqualTo(TestExceptionMessage));
             }
             else
             {
@@ -395,7 +395,7 @@ public void As_Object_AffectedByDecoders()
 
             var pyObj = PythonEngine.Eval("iter");
             var decoded = pyObj.As<object>();
-            Assert.AreSame(everythingElseToSelf, decoded);
+            Assert.That(decoded, Is.SameAs(everythingElseToSelf));
         }
 
         public class EverythingElseToSelfDecoder : IPyObjectDecoder

diff --git a/src/embed_tests/Dynamic.cs b/src/embed_tests/Dynamic.cs
@@ -19,12 +19,12 @@ public void AssignObject()
             sys.testattr = stream;
             // Check whether there are the same object.
             dynamic _stream = sys.testattr.AsManagedObject(typeof(StringBuilder));
-            Assert.AreEqual(_stream, stream);
+            Assert.That(_stream, Is.EqualTo(stream));
 
             PythonEngine.RunSimpleString(
                 "import sys\n" +
                 "sys.testattr.Append('Hello!')\n");
-            Assert.AreEqual(stream.ToString(), "Hello!");
+            Assert.That(stream.ToString(), Is.EqualTo("Hello!"));
         }
 
         /// <summary>
@@ -45,25 +45,15 @@ public void AssignNone()
         /// Check whether we can get the attr of a python object when the
         /// value of attr is a PyObject.
         /// </summary>
-        /// <remarks>
-        /// FIXME: Issue on Travis PY27: Error : Python.EmbeddingTest.dynamicTest.AssignPyObject
-        /// Python.Runtime.PythonException : ImportError : /home/travis/virtualenv/python2.7.9/lib/python2.7/lib-dynload/_io.so: undefined symbol: _PyLong_AsInt
-        /// </remarks>
         [Test]
         public void AssignPyObject()
         {
-            if (Environment.GetEnvironmentVariable("TRAVIS") == "true" &&
-                Environment.GetEnvironmentVariable("TRAVIS_PYTHON_VERSION") == "2.7")
-            {
-                Assert.Ignore("Fails on Travis/PY27: ImportError: ... undefined symbol: _PyLong_AsInt");
-            }
-
             dynamic sys = Py.Import("sys");
             dynamic io = Py.Import("io");
             sys.testattr = io.StringIO();
             dynamic bb = sys.testattr; // Get the PyObject
             bb.write("Hello!");
-            Assert.AreEqual(bb.getvalue().ToString(), "Hello!");
+            Assert.That(bb.getvalue().ToString(), Is.EqualTo("Hello!"));
         }
 
         /// <summary>
@@ -87,7 +77,7 @@ public void PassObjectInPython()
                 "import sys\n" +
                 "sys.testattr3 = sys.testattr1 is sys.testattr2\n"
             );
-            Assert.AreEqual(sys.testattr3.ToString(), "True");
+            Assert.That(sys.testattr3.ToString(), Is.EqualTo("True"));
 
             // Compare in .NET
             Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));
@@ -110,7 +100,7 @@ public void PassPyObjectInNet()
                 "sys.testattr3 = sys.testattr1 is sys.testattr2\n"
             );
 
-            Assert.AreEqual(sys.testattr3.ToString(), "True");
+            Assert.That(sys.testattr3.ToString(), Is.EqualTo("True"));
 
             // Compare in .NET
             Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));

diff --git a/src/embed_tests/Events.cs b/src/embed_tests/Events.cs
@@ -31,7 +31,7 @@
 gc.collect()
 ");
         Runtime.Runtime.TryCollectingGarbage(10);
-        Assert.AreEqual(0, ClassWithEventHandler.alive);
+        Assert.That(ClassWithEventHandler.alive, Is.EqualTo(0));
     }
 }
 
@@ -39,7 +39,7 @@
 {
    internal static int alive;

    public event EventHandler LeakEvent;
    private Array arr;  // dummy array to exacerbate memory leak

    public ClassWithEventHandler()

diff --git a/src/embed_tests/Modules.cs b/src/embed_tests/Modules.cs
@@ -149,11 +149,11 @@ public void TestScopeClass()
                 );
                 dynamic obj1 = _ps.Class1(20);
                 var result = obj1.call(10).As<int>();
-                Assert.AreEqual(130, result);
+                Assert.That(result, Is.EqualTo(130));
 
                 obj1.update(10);
                 result = ps.Get<int>("bb");
-                Assert.AreEqual(30, result);
+                Assert.That(result, Is.EqualTo(30));
             }
         }
 
@@ -185,11 +185,11 @@ public void TestCreateVirtualPackageStructure()
 
                 dynamic obj1 = ps2.Class1(20);
                 var result = obj1.call(10).As<int>();
-                Assert.AreEqual(130, result);
+                Assert.That(result, Is.EqualTo(130));
 
                 obj1.update(10);
                 result = ps2.Get<int>("bb");
-                Assert.AreEqual(30, result);
+                Assert.That(result, Is.EqualTo(30));
             }
         }
 
@@ -229,7 +229,7 @@ public void TestImportModule()
                 var value1 = ps.Eval<int>("sys.attr1");
                 var value2 = sys.attr1.As<int>();
                 Assert.That(value1, Is.EqualTo(2));
-                Assert.AreEqual(2, value2);
+                Assert.That(value2, Is.EqualTo(2));
 
                 //import as
                 ps.Import("sys", "sys1");
@@ -308,16 +308,16 @@ public void TestImportScopeFunction()
                     dynamic func2 = scope.Get("func2");
 
                     var result1 = func2().As<int>();
-                    Assert.AreEqual(0, result1);
+                    Assert.That(result1, Is.EqualTo(0));
 
                     scope.Set("cc", 20);//it has no effect on the globals of 'func1'
                     var result2 = func2().As<int>();
-                    Assert.AreEqual(-10, result2);
+                    Assert.That(result2, Is.EqualTo(-10));
                     scope.Set("cc", 10); //rollback
 
                     ps.Set("cc", 20);
                     var result3 = func2().As<int>();
-                    Assert.AreEqual(10, result3);
+                    Assert.That(result3, Is.EqualTo(10));
                     ps.Set("cc", 10); //rollback
                 }
             }
@@ -437,7 +437,7 @@ public void TestCreate()
             scope.Execute(code);
 
             Assert.That(scope.TryGet("x", out dynamic x), Is.True);
-            Assert.AreEqual("True", x.ToString());
+            Assert.That(x.ToString(), Is.EqualTo("True"));
         }
 
         [Test]

diff --git a/src/embed_tests/NeedsReinit/TestDomainReload.cs b/src/embed_tests/NeedsReinit/TestDomainReload.cs
@@ -146,8 +146,8 @@ public override ValueType Execute(ValueType arg)
 ");
                             }
                             var clrObj = obj.As<Domain.MyClass>();
-                            Assert.AreEqual(clrObj.Property, 2);
-                            Assert.AreEqual(clrObj.Field, 20);
+                            Assert.That(2, Is.EqualTo(clrObj.Property));
+                            Assert.That(20, Is.EqualTo(clrObj.Field));
                         }
                     }
                 }

diff --git a/src/embed_tests/NeedsReinit/TestPyInitialize.cs b/src/embed_tests/NeedsReinit/TestPyInitialize.cs
@@ -28,7 +28,7 @@ public static void LoadDefaultArgs()
             {
                 using(var argv = new PyList(Runtime.Runtime.PySys_GetObject("argv")))
                 {
-                    Assert.AreNotEqual(0, argv.Length());
+                    Assert.That(argv.Length(), Is.Not.EqualTo(0));
                 }
             }
         }

diff --git a/src/embed_tests/NeedsReinit/TestPythonEngineProperties.cs b/src/embed_tests/NeedsReinit/TestPythonEngineProperties.cs
@@ -22,7 +22,7 @@ public void SetPythonHome()
             PythonEngine.PythonHome = pythonHome;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
+            Assert.That(PythonEngine.PythonHome, Is.EqualTo(pythonHome));
             PythonEngine.Shutdown();
 
             // Restoring valid pythonhome.
@@ -45,7 +45,7 @@ public void SetPythonHomeTwice()
             PythonEngine.PythonHome = pythonHome;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
+            Assert.That(PythonEngine.PythonHome, Is.EqualTo(pythonHome));
             PythonEngine.Shutdown();
 
             PythonEngine.PythonHome = pythonHomeBackup;
@@ -65,7 +65,7 @@ public void SetPythonHomeEmptyString()
             }
             PythonEngine.PythonHome = "";
 
-            Assert.AreEqual("", PythonEngine.PythonHome);
+            Assert.That(PythonEngine.PythonHome, Is.EqualTo(""));
 
             PythonEngine.PythonHome = backup;
             PythonEngine.Shutdown();
@@ -86,7 +86,7 @@ public void SetProgramName()
             PythonEngine.ProgramName = programName;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(programName, PythonEngine.ProgramName);
+            Assert.That(PythonEngine.ProgramName, Is.EqualTo(programName));
             PythonEngine.Shutdown();
 
             PythonEngine.ProgramName = programNameBackup;
@@ -124,7 +124,7 @@ public void SetPythonPath()
             PythonEngine.PythonPath = path;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(path, PythonEngine.PythonPath);
+            Assert.That(PythonEngine.PythonPath, Is.EqualTo(path));
             if (importShouldSucceed) Py.Import(moduleName);
 
             PythonEngine.Shutdown();

diff --git a/src/embed_tests/NeedsReinit/TestRuntime.cs b/src/embed_tests/NeedsReinit/TestRuntime.cs
@@ -16,11 +16,11 @@ public static void Py_IsInitializedValue()
                 Runtime.Runtime.PyGILState_Ensure();
             }
             Runtime.Runtime.Py_Finalize();
-            Assert.AreEqual(0, Runtime.Runtime.Py_IsInitialized());
+            Assert.That(Runtime.Runtime.Py_IsInitialized(), Is.EqualTo(0));
             Runtime.Runtime.Py_Initialize();
-            Assert.AreEqual(1, Runtime.Runtime.Py_IsInitialized());
+            Assert.That(Runtime.Runtime.Py_IsInitialized(), Is.EqualTo(1));
             Runtime.Runtime.Py_Finalize();
-            Assert.AreEqual(0, Runtime.Runtime.Py_IsInitialized());
+            Assert.That(Runtime.Runtime.Py_IsInitialized(), Is.EqualTo(0));
         }
 
         [Test]
@@ -30,27 +30,27 @@ public static void RefCountTest()
             using var op = Runtime.Runtime.PyString_FromString("FooBar");
 
             // New object RefCount should be one
-            Assert.AreEqual(1, Runtime.Runtime.Refcount32(op.BorrowOrThrow()));
+            Assert.That(Runtime.Runtime.Refcount32(op.BorrowOrThrow()), Is.EqualTo(1));
 
             // Checking refcount didn't change refcount
-            Assert.AreEqual(1, Runtime.Runtime.Refcount32(op.Borrow()));
+            Assert.That(Runtime.Runtime.Refcount32(op.Borrow()), Is.EqualTo(1));
 
             // Borrowing a reference doesn't increase refcount
             BorrowedReference p = op.Borrow();
-            Assert.AreEqual(1, Runtime.Runtime.Refcount32(p));
+            Assert.That(Runtime.Runtime.Refcount32(p), Is.EqualTo(1));
 
             // Py_IncRef/Py_DecRef increase and decrease RefCount
             Runtime.Runtime.Py_IncRef(op.Borrow());
-            Assert.AreEqual(2, Runtime.Runtime.Refcount32(p));
+            Assert.That(Runtime.Runtime.Refcount32(p), Is.EqualTo(2));
             Runtime.Runtime.Py_DecRef(StolenReference.DangerousFromPointer(op.DangerousGetAddress()));
-            Assert.AreEqual(1, Runtime.Runtime.Refcount32(p));
+            Assert.That(Runtime.Runtime.Refcount32(p), Is.EqualTo(1));
 
             // XIncref/XDecref increase and decrease RefCount
 #pragma warning disable CS0618 // Type or member is obsolete. We are testing corresponding members
             Runtime.Runtime.XIncref(p);
-            Assert.AreEqual(2, Runtime.Runtime.Refcount32(p));
+            Assert.That(Runtime.Runtime.Refcount32(p), Is.EqualTo(2));
             Runtime.Runtime.XDecref(op.Steal());
-            Assert.AreEqual(1, Runtime.Runtime.Refcount32(p));
+            Assert.That(Runtime.Runtime.Refcount32(p), Is.EqualTo(1));
 #pragma warning restore CS0618 // Type or member is obsolete
 
             op.Dispose();
-Original file line number
+Diff line change
@@ Expand Up / @@ -28,7 +28,7 @@ public static void LoadDefaultArgs() @@
                 {
                     using(var argv = new PyList(Runtime.Runtime.PySys_GetObject("argv")))
                     {
-                        Assert.AreNotEqual(0, argv.Length());
+                        Assert.That(argv.Length(), Is.Not.EqualTo(0));
                     }
                 }
             }
@@ Expand Down @@