Map<String, String> result = Maps.fromProperties(testProp);
    assertTrue(result.isEmpty());
    testProp.setProperty("first", "true");

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));
    assertEquals(1, result.size());
    testProp.setProperty("second", "null");

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));

    Map<String, String> result = Maps.fromProperties(testProp);
    assertTrue(result.isEmpty());
    testProp.setProperty("first", "true");

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));
    assertEquals(1, result.size());
    testProp.setProperty("second", "null");

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));

  static final boolean GENERATE_CANCELLATION_CAUSES;

  static {
    // System.getProperty may throw if the security policy does not permit access.
    boolean generateCancellationCauses;
    try {
      generateCancellationCauses =
          Boolean.parseBoolean(
              System.getProperty("guava.concurrent.generate_cancellation_cause", "false"));
    } catch (SecurityException e) {