add tests

test/UnitTests/MSTest.Analyzers.UnitTests/UseNullableForIsNullAndIsNotNullAssertionsAnalyzerTests.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using VerifyCS = MSTest.Analyzers.Test.CSharpCodeFixVerifier<
+    MSTest.Analyzers.UseNullableForIsNullAndIsNotNullAssertionsAnalyzer,
+    Microsoft.CodeAnalysis.Testing.EmptyCodeFixProvider>;
+
+namespace MSTest.Analyzers.Test;
+
+[TestGroup]
+public sealed class UseNullableForIsNullAndIsNotNullAssertionsAnalyzerTests(ITestExecutionContext testExecutionContext) : TestBase(testExecutionContext)
+{
+    public async Task WhenIsNullAssertion_ValueParameterIsNullable_NoDiagnostic()
+    {
+        string code = """
+            using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+            [TestClass]
+            public class MyTestClass
+            {
+                [TestMethod]
+                public void MyTestMethod()
+                {
+                    string? var = null;
+                    Assert.IsNull(var);
+                }
+            }
+            """;
+
+        await VerifyCS.VerifyAnalyzerAsync(code);
+    }
+
+    public async Task WhenIsNullAssertion_ValueParameterIsNotNullable_Diagnostic()
+    {
+        string code = """
+            using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+            [TestClass]
+            public class MyTestClass
+            {
+                [TestMethod]
+                public void MyTestMethod()
+                {
+                    string var = "value";
+                    Assert.[|IsNull|](var);
+                }
+            }
+            """;
+
+        await VerifyCS.VerifyAnalyzerAsync(code);
+    }
+}