code: @Test public void test(){
    KeyFormat<Object> keyFormat=mock(KeyFormat.class);
    TwoWayKey2StringMapper mapper=new SimpleKeyFormatMapper(keyFormat);
    Object key=new Object();
    String formatted="foo";
    when(keyFormat.getTargetClass()).thenReturn(Object.class);
    when(keyFormat.format(key)).thenReturn(formatted);
    when(keyFormat.parse(formatted)).thenReturn(key);
    Assert.assertSame(formatted,mapper.getStringMapping(key));
    Assert.assertSame(key,mapper.getKeyMapping(formatted));
    Assert.assertTrue(mapper.isSupportedType(Object.class));
    Assert.assertFalse(mapper.isSupportedType(Integer.class));
  }
  