Lucene.Net.Index.TestBackwardsCompatibility.TestOldVersions C# (CSharp) Method

        public virtual void TestOldVersions()
        {
            // first create a little index with the current code and get the version
            Directory currentDir = NewDirectory();
            RandomIndexWriter riw = new RandomIndexWriter(Random(), currentDir, Similarity, TimeZone);
            riw.AddDocument(new Document());
            riw.Dispose();
            DirectoryReader ir = DirectoryReader.Open(currentDir);
            SegmentReader air = (SegmentReader)ir.Leaves[0].Reader;
            string currentVersion = air.SegmentInfo.Info.Version;
            Assert.IsNotNull(currentVersion); // only 3.0 segments can have a null version
            ir.Dispose();
            currentDir.Dispose();

            IComparer<string> comparator = StringHelper.VersionComparator;

            // now check all the old indexes, their version should be < the current version
            foreach (string name in OldNames)
            {
                Directory dir = OldIndexDirs[name];
                DirectoryReader r = DirectoryReader.Open(dir);
                foreach (AtomicReaderContext context in r.Leaves)
                {
                    air = (SegmentReader)context.Reader;
                    string oldVersion = air.SegmentInfo.Info.Version;
                    Assert.IsNotNull(oldVersion); // only 3.0 segments can have a null version
                    Assert.IsTrue(comparator.Compare(oldVersion, currentVersion) < 0, "current Constants.LUCENE_MAIN_VERSION is <= an old index: did you forget to bump it?!");
                }
                r.Dispose();
            }
        }