Fix MSTEST0037 false positive for non-int count argument

src/Analyzers/MSTest.Analyzers/UseProperAssertMethodsAnalyzer.cs

@@ -1430,6 +1430,16 @@ expectedArgument.ConstantValue.Value is int expectedValue &&
             {
                 // We have Assert.AreEqual(expectedCount, collection.Count/Length)
                 // We want Assert.HasCount(expectedCount, collection)
+                // Assert.HasCount takes int, so skip if expectedCount is not an int (e.g. int?, long, uint, decimal).
+                if (expectedArgument.Type?.SpecialType != SpecialType.System_Int32)
+                {
+                    nodeToBeReplaced1 = null;
+                    replacement1 = null;
+                    nodeToBeReplaced2 = null;
+                    replacement2 = null;
+                    return CountCheckStatus.Unknown;
+                }
+
                 // So, only a single replacement is needed. We replace collection.Count with collection.
                 nodeToBeReplaced1 = actualArgument.Syntax; // collection.Count
                 replacement1 = expression; // collection
@@ -1461,6 +1471,16 @@ expectedArgument.ConstantValue.Value is int expectedLinqValue &&
             {
                 // We have Assert.AreEqual(expectedCount, enumerable.Count())
                 // We want Assert.HasCount(expectedCount, enumerable)
+                // Assert.HasCount takes int, so skip if expectedCount is not an int (e.g. int?, long, uint, decimal).
+                if (expectedArgument.Type?.SpecialType != SpecialType.System_Int32)
+                {
+                    nodeToBeReplaced1 = null;
+                    replacement1 = null;
+                    nodeToBeReplaced2 = null;
+                    replacement2 = null;
+                    return CountCheckStatus.Unknown;
+                }
+
                 nodeToBeReplaced1 = actualArgument.Syntax; // enumerable.Count()
                 replacement1 = linqCollection; // enumerable
                 nodeToBeReplaced2 = null;

test/UnitTests/MSTest.Analyzers.UnitTests/UseProperAssertMethodsAnalyzerTests.cs

@@ -2086,6 +2086,35 @@ await VerifyCS.VerifyCodeFixAsync(
             fixedCode);
     }
 
+    [TestMethod]
+    public async Task WhenAssertAreEqualWithCollectionCountNonZeroNonIntExpected()
+    {
+        string code = """
+            using Microsoft.VisualStudio.TestTools.UnitTesting;
+            using System.Collections.Generic;
+            using System.Linq;
+
+            [TestClass]
+            public class MyTestClass
+            {
+                [TestMethod]
+                public void MyTestMethod()
+                {
+                    int? nullableCount = 3;
+                    long longCount = 3L;
+                    var list = new List<int> { 1, 2, 3 };
+                    Assert.AreEqual(nullableCount, list.Count);
+                    Assert.AreEqual(nullableCount, list.AsEnumerable().Count());
+                    Assert.AreEqual(longCount, list.Count);
+                    Assert.AreEqual(longCount, list.AsEnumerable().Count());
+                }
+            }
+            """;
+
+        // Should not trigger MSTEST0037 because Assert.HasCount takes int, not int? or long
+        await VerifyCS.VerifyAnalyzerAsync(code);
+    }
+
     [TestMethod]
     public async Task WhenAssertAreNotEqualWithCollectionCountZero()
     {