### Question:
BaseCollection extends BaseElement<R> implements ObjectInterface, Cloneable { @Override public BaseClass getXClass(XWikiContext context) { BaseClass baseClass = null; if ((context == null) || (context.getWiki() == null)) { return baseClass; } DocumentReference classReference = getXClassReference(); if (classReference != null) { try { baseClass = context.getWiki().getXClass(classReference, context); } catch (Exception e) { LOGGER.error("Failed to get class [" + classReference + "]", e); } } return baseClass; }  int getNumber(); void setNumber(int number); void addPropertyForRemoval(PropertyInterface field); DocumentReference getXClassReference(); EntityReference getRelativeXClassReference(); @Deprecated String getClassName(); void setXClassReference(EntityReference xClassReference); @Deprecated void setClassName(String name); @Override PropertyInterface safeget(String name); @Override PropertyInterface get(String name); @Override void safeput(String name, PropertyInterface property); @Override void put(String name, PropertyInterface property); @Override BaseClass getXClass(XWikiContext context); String getStringValue(String name); String getLargeStringValue(String name); void setStringValue(String name, String value); void setLargeStringValue(String name, String value); int getIntValue(String name); int getIntValue(String name, int default_value); void setIntValue(String name, int value); long getLongValue(String name); void setLongValue(String name, long value); float getFloatValue(String name); void setFloatValue(String name, float value); double getDoubleValue(String name); void setDoubleValue(String name, double value); Date getDateValue(String name); void setDateValue(String name, Date value); Set<?> getSetValue(String name); void setSetValue(String name, Set<?> value); List getListValue(String name); void setStringListValue(String name, List value); void setDBStringListValue(String name, List value); void setFields(Map fields); PropertyInterface getField(String name); void addField(String name, PropertyInterface element); void removeField(String name); Collection getFieldList(); Set<String> getPropertyList(); Object[] getProperties(); String[] getPropertyNames(); Iterator getSortedIterator(); @Override boolean equals(Object coll); @Override BaseCollection clone(); void merge(BaseObject object); List<ObjectDiff> getDiff(Object oldObject, XWikiContext context); List getFieldsToRemove(); void setFieldsToRemove(List fieldsToRemove); @Override Element toXML(); @Override @Deprecated Element toXML(BaseClass bclass); String toXMLString(); Map<String, Object> getCustomMappingMap(); @Override void setDocumentReference(DocumentReference reference); @Override void merge(ElementInterface previousElement, ElementInterface newElement, MergeConfiguration configuration,
        XWikiContext context, MergeResult mergeResult); @Override boolean apply(ElementInterface newElement, boolean clean); @Override void setOwnerDocument(XWikiDocument ownerDocument);  }### Answer:
@Test public void testGetXClassWithNullReference() throws Exception { BaseCollection collection = new BaseCollection() { @Override public Element toXML(BaseClass bclass) { return null; } }; Assert.assertNull(collection.getXClass(getContext())); }