move back to System.Collections.Immutable 8 (#181)

Author: SimonCropp

src/Directory.Build.props

@@ -2,7 +2,7 @@
 <Project>
   <PropertyGroup>
     <NoWarn>CS1591;CS0649;NU5119</NoWarn>
-    <Version>8.5.1</Version>
+    <Version>8.6.0</Version>
     <LangVersion>preview</LangVersion>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <Description>A collection of minimal binary files.</Description>

src/Directory.Packages.props

@@ -10,7 +10,7 @@
     <PackageVersion Include="NUnit3TestAdapter" Version="4.6.0" />
     <PackageVersion Include="Polyfill" Version="7.5.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.147" />
-    <PackageVersion Include="System.Collections.Immutable" Version="9.0.0" />
+    <PackageVersion Include="System.Collections.Immutable" Version="8.0.0" />
     <PackageVersion Include="System.Memory" Version="4.6.0" />
   </ItemGroup>
 </Project>

src/Tests/GlobalUsings.cs

@@ -1,2 +1,3 @@
 global using EmptyFiles;
-global using NUnit.Framework;
+global using NUnit.Framework;
+global using System.Collections.Immutable;

src/Tests/ImmutableVersionTests.cs

@@ -0,0 +1,14 @@
+#if NETFRAMEWORK
+
+public class ImmutableVersionTests
+{
+    // work around https://github.com/orgs/VerifyTests/discussions/1366
+    [Test]
+    public void AssertVersion()
+    {
+        var assemblyName = typeof(ImmutableDictionary).Assembly.GetName();
+        AreEqual(new Version(8, 0, 0, 0), assemblyName.Version);
+    }
+}
+
+#endif

src/Tests/IndexWriter.cs

@@ -1,4 +1,5 @@
-public class IndexWriter
+#if NET9_0
+public class IndexWriter
 {
     static List<KeyValuePair<string, EmptyFile>> files = null!;
 
@@ -7,7 +8,6 @@ public static void Init() =>
         files = AllFiles
             .Files.OrderBy(_ => _.Key)
             .ToList();
-
     [Test]
     public void CreateIndex() =>
         InnerCreateIndex();
@@ -27,4 +27,5 @@ static void InnerCreateIndex([CallerFilePath] string filePath = "")
             File.Copy(value.Path, Path.Combine(indexPath, $"empty{key}"));
         }
     }
-}
+}
+#endif