### Question:
TSNameSpace { public TSNameSpace findOrCreate(String namespace) { requireNonNull(namespace, "namespace"); if (this.name.equals(namespace)) return this; final String car = StringUtils.car(namespace); final Optional<String> cdr = StringUtils.cdr(namespace); final TSNameSpace child; if (this.children.containsKey(car)) { child = this.children.get(car); } else { child=new TSNameSpace(car); this.children.put(car,child); } return cdr.map(child::findOrCreate).orElse(child); } private  TSNameSpace(String name, List<TSType> types, Map<String, TSNameSpace> children);  TSNameSpace(); private  TSNameSpace(String name); TSNameSpace findOrCreate(String namespace); void addType(TSType type); @Override String toString(); boolean isRoot(); String getName(); List<TSType> getTypes(); Set<String> getSubNamespaces(); TSNameSpace getSubNameSapce(String thatName);  }### Answer:
@Test @DisplayName("TSNamespace: Check namespace not null") void test_findOrCreateAssertion() { assertThrows(NullPointerException.class, () -> new TSNameSpace().findOrCreate(null) ); }