### Question:
JsonMapConverter implements AttributeConverter<Map<String, Object>, String> { @Override public String convertToDatabaseColumn(final Map<String, Object> map) { if (map == null) { return null; } try { return Json.getObjectMapper().writeValueAsString(map); } catch (final JsonProcessingException ex) { throw new MinijaxException(ex.getMessage(), ex); } }  @Override String convertToDatabaseColumn(final Map<String, Object> map); @Override @SuppressWarnings("unchecked") Map<String, Object> convertToEntityAttribute(final String str);  }### Answer:
@Test(expected = MinijaxException.class) public void testInvalidJsonWrite() { final JsonMapConverter c = new JsonMapConverter(); final Map<String, Object> m1 = new HashMap<>(); m1.put("a", new Object()); c.convertToDatabaseColumn(m1); }