Adjust for culture name normalization in AssemblyNameInfoFuzzer (#114231)

* add a test with comment that explains the unexpected behavior

* adjust the AssemblyNameInfoFuzzer

* mention normalization as well

Author: adamsitnik

src/libraries/Fuzzing/DotnetFuzzing/Fuzzers/AssemblyNameInfoFuzzer.cs

@@ -61,9 +61,21 @@ private static void Test(Span<char> span)
                 Assert.Equal(fromTryParse.ToAssemblyName().CultureName, fromParse.ToAssemblyName().CultureName);
 
                 Assert.Equal(fromTryParse.Name, fromParse.ToAssemblyName().Name);
-                Assert.Equal(fromTryParse.CultureName, fromParse.ToAssemblyName().CultureName);
                 Assert.Equal(fromTryParse.Version, fromParse.ToAssemblyName().Version);
 
+                if (fromTryParse.CultureName is not null)
+                {
+                    // When converting to AssemblyName, the culture name is lower-cased
+                    // by the CultureInfo ctor that calls CultureData.GetCultureData
+                    // which lowers the name for caching and normalization purposes.
+                    Assert.Equal(fromTryParse.CultureName.ToLower(), fromParse.ToAssemblyName().CultureName);
+                }
+                else
+                {
+                    Assert.True(fromParse.ToAssemblyName().CultureName is null);
+                }
+                
+
                 // AssemblyNameInfo.FullName can be different than AssemblyName.FullName:
                 // AssemblyNameInfo includes public key, AssemblyName only its Token.
 

src/libraries/System.Reflection.Metadata/tests/Metadata/AssemblyNameInfoTests.cs

@@ -105,6 +105,17 @@ public void EmptyInputIsInvalid()
             Assert.Throws<ArgumentException>(() => AssemblyNameInfo.Parse("".AsSpan()));
         }
 
+        [Fact]
+        public void CultureNameGetLoweredByToAssemblyName()
+        {
+            AssemblyNameInfo assemblyNameInfo = AssemblyNameInfo.Parse("test,culture=aA".AsSpan());
+            Assert.Equal("aA", assemblyNameInfo.CultureName);
+            // When converting to AssemblyName, the culture name is lower-cased
+            // by the CultureInfo ctor that calls CultureData.GetCultureData
+            // which lowers the name for caching and normalization purposes.
+            Assert.Equal("aa", assemblyNameInfo.ToAssemblyName().CultureName);
+        }
+
         static void Roundtrip(AssemblyName source)
         {
             AssemblyNameInfo parsed = AssemblyNameInfo.Parse(source.FullName.AsSpan());