Test isolation and temporary files

A test that writes files should work in a disposable directory. tempfile.TemporaryDirectory cleans up after the with block, while pathlib makes the path explicit.

Worked example

from pathlib import Path
from tempfile import TemporaryDirectory
with TemporaryDirectory() as folder:
    file = Path(folder) / "note.txt"
    file.write_text("study", encoding="utf-8")
    print(file.read_text(encoding="utf-8"))
print(file.exists())

study
False

Why this works

The context manager removes its temporary directory on exit. The file path object still exists as a value, but the file no longer exists.

Another case

from tempfile import TemporaryDirectory
from pathlib import Path
with TemporaryDirectory() as folder:
    path = Path(folder) / "count.txt"
    path.write_text("2", encoding="utf-8")
    print(int(path.read_text(encoding="utf-8")) + 1)

3

Practice

Write two lines to a temporary file and assert its read_text result inside the with block.

Try another case

Where does Path(folder) point inside the with block, and what happens to it afterwards?