### Question:
PropertiesHolder implements IHasProperties { @Override public boolean containsKey( String key ) { if ( properties == null ) { return false; } else { return properties.containsKey( key ); } } PropertiesHolder(); @Override Object getProperty( String key ); String getPropertyAsString( String key ); @Override void setProperty( String key, Object value ); @Override Object removeProperty( String key ); @Override Set<String> getPropertyKeys(); @Override Map<String, Object> getProperties(); @Override void setProperties( Map<String, Object> props ); @Override void removeProperties( Set<String> keys ); @Override void clearProperties(); @Override boolean containsKey( String key ); @Override boolean isDirty(); @Override void setDirty( boolean dirty ); @Override String toString();  }### Answer:
@Test public void testContainsKey_nullProperties() throws Exception { props.properties = null; assertFalse( props.containsKey( "nope" ) ); }