File system testing with tmp_path in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest tmp_path file creation

What will be the output of this pytest test when run?

def test_create_file(tmp_path):
    file = tmp_path / "test.txt"
    file.write_text("hello")
    content = file.read_text()
    print(content)
    assert content == "hello"

PyTest

def test_create_file(tmp_path):
    file = tmp_path / "test.txt"
    file.write_text("hello")
    content = file.read_text()
    print(content)
    assert content == "hello"

A Prints 'hello' but test fails

B Prints 'hello' and test passes

C Raises FileNotFoundError

D Prints empty string and test fails

💡 Hint

tmp_path creates a temporary directory unique to the test.

The tmp_path fixture provides a temporary directory. Writing and reading the file works as expected, so 'hello' is printed and the assertion passes.

❓ assertion

intermediate

Correct assertion for file existence with tmp_path

Which assertion correctly checks that a file named 'data.csv' exists in the tmp_path directory?

PyTest

def test_file_exists(tmp_path):
    file = tmp_path / "data.csv"
    file.write_text("id,name\n1,Alice")
    # Which assertion is correct here?

A assert file.read_text() == ''

B assert file.is_file()

C assert tmp_path.exists()

D assert file.exists()

💡 Hint

Check if the file path exists on the filesystem.

file.exists() returns True if the file exists. file.is_file() returns True only if the path points to a regular file. tmp_path.exists() checks the directory, not the file. The last option checks content, not existence.

🔧 Debug

advanced

Debug failing test with tmp_path and file write

This test fails with an error. What is the cause?

def test_write_file(tmp_path):
    file = tmp_path / "output.txt"
    file.write("data")
    assert file.read_text() == "data"

PyTest

def test_write_file(tmp_path):
    file = tmp_path / "output.txt"
    file.write("data")
    assert file.read_text() == "data"

A read_text() returns bytes, causing assertion failure

B File path is incorrect, should use str(file)

C write() is not a method on pathlib.Path, should use write_text()

D tmp_path is read-only, cannot write files

💡 Hint

Check pathlib.Path methods for writing text.

pathlib.Path objects do not have a write() method. The correct method to write text is write_text(). Using write() causes AttributeError.

🧠 Conceptual

advanced

Why use tmp_path over tmpdir in pytest?

Which reason best explains why pytest recommends using tmp_path instead of tmpdir for file system tests?

A tmp_path provides pathlib.Path objects which are more modern and easier to use

B tmpdir creates files in the system root directory causing permission errors

C tmp_path runs tests faster by caching files between tests

D tmpdir does not clean up files after tests finish

💡 Hint

Consider the type of object returned by each fixture.

tmp_path returns pathlib.Path objects which have a rich API and are preferred in modern Python. tmpdir returns py.path.local objects which are older and less standard.

❓ framework

expert

Handling cleanup of nested directories with tmp_path

In a pytest test using tmp_path, you create nested directories and files:

def test_nested(tmp_path):
    nested_dir = tmp_path / "a" / "b" / "c"
    nested_dir.mkdir(parents=True)
    file = nested_dir / "file.txt"
    file.write_text("content")
    # After test finishes, what happens to these files and directories?

A All files and directories under tmp_path are deleted automatically after the test

B Only the top-level tmp_path directory is deleted, nested files remain

C Files remain but directories are deleted, causing orphan files

D Nothing is deleted automatically; manual cleanup is required

💡 Hint

pytest tmp_path fixture manages cleanup automatically.

pytest tmp_path creates a temporary directory unique to the test and deletes it entirely after the test finishes, including all nested files and directories.