After a while, we might end up with a pretty good suite of characterization tests for the legacy code. We can now approach this code like any other well-tested code and start applying the bigger refactorings with an aim to improve the design before adding our new features.
For example, we might decide to extract the print_action method into a separate Action class, or the parse_file method into a Reader class.
The following is a FileReader class where we have moved the contents from the parse_file local method:
class FileReader:
def __init__(self, filename):
self.filename = filename
def get_updates(self):
updates = []
with open("updates.csv", "r") as fp:
for line in fp.readlines():
symbol, timestamp, price = line.split(",")
updates.append((symbol, datetime.strptime(timestamp, "%Y-%m-%dT%H:%M:%S.%f"), int(price)))
return updatesWe then use the Inject Dependencies pattern to pass the reader as...