### Question:
Customer extends StripeJsonModel { @Nullable public static Customer fromString(String jsonString) { if (jsonString == null) { return null; } try { return fromJson(new JSONObject(jsonString)); } catch (JSONException ignored) { return null; } } private  Customer(); String getId(); String getDefaultSource(); ShippingInformation getShippingInformation(); List<CustomerSource> getSources(); Boolean getHasMore(); Integer getTotalCount(); String getUrl(); @Nullable CustomerSource getSourceById(@NonNull String sourceId); @NonNull @Override JSONObject toJson(); @NonNull @Override Map<String, Object> toMap(); @Nullable static Customer fromString(String jsonString); @Nullable static Customer fromJson(JSONObject jsonObject);  }### Answer:
@Test public void fromString_whenStringIsNull_returnsNull() { assertNull(Customer.fromString(null)); }
@Test public void fromJson_whenNotACustomer_returnsNull() { assertNull(Customer.fromString(NON_CUSTOMER_OBJECT)); }