NavigableMap<String, String> innermost = new SafeTreeMap<>();
                    for (Entry<String, String> entry : entries) {
                      innermost.put(entry.getKey(), entry.getValue());
                    }
                    TestMap<String, String> inner = new TestMap<>(innermost, mutex);

        @Test
        @DisplayName("Should handle deeply nested exceptions")
        void testToStringWithNestedExceptions() {
            Exception innermost = new IOException("Innermost exception");
            Exception middle = new RuntimeException("Middle exception", innermost);
            Exception rootCause = new IllegalStateException("Outer exception", middle);

  @GwtIncompatible
  @Deprecated
  public static RuntimeException propagate(Throwable throwable) {
    throwIfUnchecked(throwable);
    throw new RuntimeException(throwable);
  }

  /**
   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>

    for (int i = 0; i < 100000; i++) {
      SettableFuture<String> curr = SettableFuture.create();
      prev.setFuture(curr);
      prev = curr;
    }
    // prev represents the 'innermost' future
    prev.set("done");
    assertTrue(orig.isDone());
  }

  // Verify that StackOverflowError in a long chain of SetFuture doesn't cause the entire toString
  // call to fail
  @J2ktIncompatible