### Question:
ImmutableNamespaces implements Namespaces { @Override public String getPrefix(String namespaceURI) { for(Entry<String,String> entry:this.map.entrySet()) { if(entry.getValue().equals(namespaceURI)) { return entry.getKey(); } } return null; } private  ImmutableNamespaces(Map<String,String> map);  ImmutableNamespaces(); ImmutableNamespaces withPrefix(String prefix, String namespaceURI); ImmutableNamespaces withoutPrefix(String... prefixes); @Override Set<String> getDeclaredPrefixes(); @Override String getNamespaceURI(String prefix); @Override String getPrefix(String namespaceURI); @Override List<String> getPrefixes(String namespaceURI); @Override String toString();  }### Answer:
@Test public void testGetPrefix$found() throws Exception { assertThat(this.sut.getPrefix(DEFAULT_NAMESPACE),anyOf(equalTo(DEFAULT_PR1),equalTo(DEFAULT_PR2))); }
@Test public void testGetPrefix$notFound() throws Exception { assertThat(this.sut.getPrefix("not found"),nullValue()); }