code: package com.beijunyi.parallelgit.filesystem;
  
  import java.io.IOException;
  import java.net.URI;
  import java.nio.file.FileSystemNotFoundException;
  
  import com.beijunyi.parallelgit.filesystem.utils.GfsUriBuilder;
  import org.junit.Test;
  
  import static org.junit.Assert.assertEquals;
  
  public class GitFileSystemProviderGetFileSystemTest extends PreSetupGitFileSystemTest {
  
    @Test
    public void getFileSystemForUri_theResultShouldBeTheCorrespondingFileSystem() throws IOException {
      URI uri = root.toUri();
      GitFileSystem result = provider.getFileSystem(uri);
      assertEquals(gfs, result);
    }
  
    @Test(expected = FileSystemNotFoundException.class)
    public void getFileSystemForUriWithInvalidSessionId_shouldThrowFileSystemNotFoundException() {
      URI uri = GfsUriBuilder.fromFileSystem(gfs)
                  .sid("some_invalid_sid")
                  .build();
      provider.getFileSystem(uri);
    }
  
    @Test(expected = FileSystemNotFoundException.class)
    public void getFileSystemForUriWithNoSessionId_shouldThrowFileSystemNotFoundException() {
      URI uri = GfsUriBuilder.fromFileSystem(gfs)
                  .sid(null)
                  .build();
      provider.getFileSystem(uri);
    }
  }
  