public static String substVars(String val, PropertyContainer pc1) {
    return substVars(val, pc1, null);
  }
@Test
  public void testSubstVarsTwoLevelsWithDefault() {
    // Example input taken from LOGBCK-943 bug report
    context.putProperty("APP_NAME", "LOGBACK");
    context.putProperty("ARCHIVE_SUFFIX", "archive.log");
    context.putProperty("LOG_HOME", "${logfilepath.default:-logs}");
    context.putProperty("ARCHIVE_PATH", "${LOG_HOME}/archive/${APP_NAME}");

    String result = OptionHelper.substVars("${ARCHIVE_PATH}_trace_${ARCHIVE_SUFFIX}", context);
    assertEquals("logs/archive/LOGBACK_trace_archive.log", result);
  }