fileinput.input 的单元测试

Question

I have some code I'm trying to write a unit test for.

This is the function I have:

def sanitize_text():
    total_text = []

    # Regex split to strip non-alphanumeric characters
    for line in fileinput.input():
        line.casefold()
        words = [x for x in re.split("\W",line) if x]
        total_text += words

    return total_text

My intention is to have this function work with an unspecified number of files passed in as an argument, or with stdin, so fileinput seemed like a good way to do that.

However, I can't figure out how to write a unit test for this, mainly because I can't figure out how to pass this function "fake" input.

I've tried using mock patch and opening a fake file, but it doesn't seem to get passed to the function properly. I've also tried using mock patch to spoof sys.argv[1] , but that only lets me spoof a file name, not the content.

What's a good way to fool this function into accepting fake input for the sake of the unit test?

Answer 1

You said this code is not in its final shape yet, so I will focus only on the part about how to pass "fake input". One commonly useful trick is to separate the part of your code that does the calculations from the part that is interacting with other code/libraries/IO:

def add_sanitized_line(text, line):
    line.casefold()
    # Regex split to strip non-alphanumeric characters
    words = [x for x in re.split("\W",line) if x]
    text += words

This function can be nicely unit-tested without need for mocking. You provide it "fake input" by passing any kind of input for line you consider necessary.