I asked this question about how to write a pytest to check output in stdout and got a solution. Now I need to write a test case, to check if the contents are written to the file and that the contents are written as expected

eg:

def writetoafile():

file = open("output.txt",w)

file.write("hello\n")

file.write("world\n")

file.close()

now a pytest function to check if it written:

def test_writeToFile():

file = open("ouput.txt",'r')

expected = "hello\nworld\n"

assert expected==file.read()

while this seems to work, I do not think this is ideal, especially hard-coding. how are these kind of test functions of writing to a file usually written?

解决方案

There is the tmpdir fixture which will create you a per-test temporary directory. So a test would look something like this:

def writetoafile(fname):

with open(fname, 'w') as fp:

fp.write('Hello\n')

def test_writetofile(tmpdir):

file = tmpdir.join('output.txt')

writetoafile(file.strpath) # or use str(file)

assert file.read() == 'Hello\n'

Here you're refactoring the code to not be hardcoded either, which is a prime example of how testing your code makes you design it better.