// Add failure test case.
	testCases = append(testCases, struct {
		partNum       int
		expectedIndex int
	}{6, -1})

	// Test them.
	for _, testCase := range testCases {
		if index := objectPartIndex(fi.Parts, testCase.partNum); index != testCase.expectedIndex {
			t.Fatalf("%+v: expected = %d, got: %d", testCase, testCase.expectedIndex, index)
		}
	}
}

// Test FileInfo.ObjectToPartOffset().

        Multimaps.index(stringToObject.values().iterator(), Functions.toStringFunction());
    assertEquals(stringToObject, outputMap);
  }

  public void testIndex_ordering() {
    final Multimap<Integer, String> expectedIndex =
        new ImmutableListMultimap.Builder<Integer, String>()
            .put(4, "Inky")
            .put(6, "Blinky")
            .put(5, "Pinky")
            .put(5, "Pinky")
            .put(5, "Clyde")

        Multimaps.index(stringToObject.values().iterator(), Functions.toStringFunction());
    assertEquals(stringToObject, outputMap);
  }

  public void testIndex_ordering() {
    final Multimap<Integer, String> expectedIndex =
        new ImmutableListMultimap.Builder<Integer, String>()
            .put(4, "Inky")
            .put(6, "Blinky")
            .put(5, "Pinky")
            .put(5, "Pinky")
            .put(5, "Clyde")