void () { FileTypeAssocTable<FileTypeManagerImpl.FileTypeWithDescriptor> table = myFileTypeManager.getExtensionMap().copy(); FileTypeManagerImpl.FileTypeWithDescriptor fileType = FileTypeManagerImpl.coreDescriptorFor(ArchiveFileType.INSTANCE); FileNameMatcher matcher = table.getAssociations(fileType).get(0); table.removeAssociation(matcher, fileType); Map<FileNameMatcher, FileTypeManagerImpl.FileTypeWithDescriptor> reassigned = myFileTypeManager.getExtensionMap().getRemovedMappings(table, myFileTypeManager.getRegisteredFileTypeWithDescriptors()); assertEquals(1, reassigned.size()); }