@Test
  public void testFileSystem() {
    assertThat(fs.getSeparator()).isEqualTo("/");
    assertThat(fs.getRootDirectories())
        .containsExactlyElementsIn(ImmutableSet.of(path("/")))
        .inOrder();
    assertThat(fs.isOpen()).isTrue();
    assertThat(fs.isReadOnly()).isFalse();
    assertThat(fs.supportedFileAttributeViews()).containsExactly("basic", "owner", "posix", "unix");
    assertThat(fs.provider()).isInstanceOf(JimfsFileSystemProvider.class);
  }
Tests an in-memory file system through the public APIs in {@link Files}, etc. This also acts as
the tests for {@code FileSystemView}, as each public API method is (mostly) implemented by a
method in {@code FileSystemView}.

<p>These tests uses a Unix-like file system, but most of what they test applies to any file
system configuration.

@author Colin Decker
jimfs/src/test/java/com/google/common/jimfs/JimfsUnixLikeFileSystemTest.java