@Test
  public void testPutEntryForExistingNameIsIllegal() {
    dir.put(entry("foo"));

    try {
      dir.put(entry("foo"));
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }
Tests for {@link Directory}.

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