### Question:
SubConfiguration implements Configuration { public void setPrefix(String newPrefix){ prefix = newPrefix; } SubConfiguration();  SubConfiguration(Configuration cfg, String prefix); void setConfiguration(Configuration newCfg); void setPrefix(String newPrefix); String get(String propertyName); String[] getAll(String propertyName); int[] getInts(String propertyName); long[] getLongs(String propertyName); double[] getDoubles(String propertyName); boolean[] getBooleans(String propertyName); String get(String propertyName, String defaultValue); boolean getBoolean(String propertyName); boolean getBoolean(String propertyName, boolean defaultValue); double getDouble(String propertyName); double getDouble(String propertyName, double defaultValue); long getLong(String propertyName); long getLong(String propertyName, long defaultValue); int getInt(String propertyName); int getInt(String propertyName, int defaultValue); void put(String name, Object value); Object getObject(String propertyName); @Override Set<String> keySet();  }### Answer:
@Test public void testSetPrefix() throws Throwable { SubConfiguration subConfiguration = new SubConfiguration(); subConfiguration.setPrefix("testSubConfigurationNewPrefix"); assertEquals("testSubConfigurationNewPrefix", subConfiguration.prefix, "subConfiguration.prefix"); }