testing nullable operators in interfaces

src/NServiceBus.Core.Tests/API/Infra/NullableInterface/ITestInterface.cs

@@ -0,0 +1,13 @@
+#nullable enable
+
+namespace NServiceBus.Core.Tests.API.Infra.NullableInterface
+{
+    interface ITestInterface
+    {
+        string WriteAMessage(string message);
+
+        string WriteNullableMessage(string? message);
+
+        string? ReturnNullableMessage(string? message);
+    }
+}

src/NServiceBus.Core.Tests/API/Infra/NullableInterface/TestInterface.cs

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+namespace NServiceBus.Core.Tests.API.Infra.NullableInterface
+{
+    using System;
+
+    class TestInterface : ITestInterface
+    {
+        public string ReturnNullableMessage(string message)
+        {
+            Console.WriteLine(message);
+            return message;
+        }
+
+        public string WriteAMessage(string message)
+        {
+            Console.WriteLine(message);
+            return message;
+        }
+        public string WriteNullableMessage(string message)
+        {
+            Console.WriteLine(message);
+            return message;
+        }
+    }
+}

src/NServiceBus.Core.Tests/API/Infra/NullableInterface/TestInterfaceTest.cs

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+namespace NServiceBus.Core.Tests.API.Infra.NullableInterface
+{
+    using NUnit.Framework;
+
+    class TestInterfaceTest
+    {
+        [Test]
+        public void Test_with_no_nullable_operators()
+        {
+            var testInterface = new TestInterface();
+            var message = "Hello, World!";
+            var nullableMessage = (string)null;
+            // Test WriteAMessage
+            var result1 = testInterface.WriteAMessage(message);
+            Assert.That(result1, Is.EqualTo(message));
+            // Test WriteNullableMessage with non-null value
+            var result2 = testInterface.WriteNullableMessage(message);
+            Assert.That(result2, Is.EqualTo(message));
+            // Test WriteNullableMessage with null value
+            var result3 = testInterface.WriteNullableMessage(nullableMessage);
+            Assert.That(result3, Is.EqualTo(nullableMessage));
+            // Test ReturnNullableMessage with non-null value
+            var result4 = testInterface.ReturnNullableMessage(message);
+            Assert.That(result4, Is.EqualTo(message));
+            // Test ReturnNullableMessage with null value
+            var result5 = testInterface.ReturnNullableMessage(nullableMessage);
+            Assert.That(result5, Is.EqualTo(nullableMessage));
+        }
+    }
+}

src/NServiceBus.Core.Tests/API/Infra/NullableInterface/TestInterfaceTest_Nullable.cs

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+#nullable enable
+
+namespace NServiceBus.Core.Tests.API.Infra.NullableInterface
+{
+    using NUnit.Framework;
+
+    class TestInterfaceTest_Nullable
+    {
+        [Test]
+        public void Test_with_no_nullable_operators()
+        {
+            var testInterface = new TestInterface();
+            var message = "Hello, World!";
+            var nullableMessage = (string)null;
+            // Test WriteAMessage
+            var result1 = testInterface.WriteAMessage(message);
+            Assert.That(result1, Is.EqualTo(message));
+            // Test WriteNullableMessage with non-null value
+            var result2 = testInterface.WriteNullableMessage(message);
+            Assert.That(result2, Is.EqualTo(message));
+            // Test WriteNullableMessage with null value
+            var result3 = testInterface.WriteNullableMessage(nullableMessage);
+            Assert.That(result3, Is.EqualTo(nullableMessage));
+            // Test ReturnNullableMessage with non-null value
+            var result4 = testInterface.ReturnNullableMessage(message);
+            Assert.That(result4, Is.EqualTo(message));
+            // Test ReturnNullableMessage with null value
+            var result5 = testInterface.ReturnNullableMessage(nullableMessage);
+            Assert.That(result5, Is.EqualTo(nullableMessage));
+        }
+    }
+}