[Pytest] Fixture

Fixtures are functions that run before or after tests, like setup or teardown. Fixtures are used for data configuration, initialization, database connection/disconnection, etc.

Scope

1. Function (Run once per test)

• Function base test cases

import pytest

@pytest.fixture(scope="function")
def init_funtion():
  print("INIT")

def test_case1(init_funtion):
  print("Case1")

def test_case2(init_funtion):
  print("Case2")

""" 
Result 
"""
# INIT
# Case1
# INIT
# Case2

• Class base test cases

import pytest

@pytest.fixture(scope="function")
def init_funtion():
  print("INIT")

class TestCases():
  def test_case1(self, init_funtion):
    print("Case1")

  def test_case2(self, init_funtion):
    print("Case2")

""" 
Result 
"""
# INIT
# Case1
# INIT
# Case2

2. Class (Run once per class of tests)

• Function base test cases

import pytest

@pytest.fixture(scope="class")
def init_funtion():
  print("INIT")

def test_case1(init_funtion):
  print("Case1")

def test_case2(init_funtion):
  print("Case2")

""" 
Result 
"""
# INIT
# Case1
# Case2

• Class base test cases

import pytest

@pytest.fixture(scope="class")
def init_funtion():
  print("INIT")

class TestCases():
  def test_case1(self, init_funtion):
    print("Case1")

  def test_case2(self, init_funtion):
    print("Case2")

""" 
Result 
"""
# INIT
# Case1
# Case2

• Function base and Class base test cases

import pytest

@pytest.fixture(scope="class")
def init_funtion():
  print("INIT")

def test_case1(init_funtion):
  print("Case1")

class TestCases():
  def test_case2(self, init_funtion):
    print("Case2")
  
""" 
Result 
"""
# INIT
# Case1
# INIT
# Case2

3. Module (Run once per module)

import pytest

@pytest.fixture(scope="module")
def init_funtion():
  print("INIT")

def test_case1(init_funtion):
  print("Case1")

class TestCases():
  def test_case2(self, init_funtion):
    print("Case2")
  
""" 
Result 
"""
# INIT
# Case1
# Case2

4. Session (Run once per session)

• Set fixture in conftest.py, and can run globally.
• conftest.py

# conftest.py

import pytest

@pytest.fixture(scope="session")
def init_funtion():
  print("INIT")

• test_case1.py

# test_case1.py

def test_case1(init_funtion):
  print("Case1")

• test_case2.py

# test_case2.py

class TestCases():
  def test_case2(self, init_funtion):
    print("Case2")

• Result

""" 
Result 
"""
# INIT
# Case1
# Case2

Setup / Teardown

1. yield

• The part before yield will execute at the beginning of test.
• The part after yield will execute at the end of test.

import pytest

@pytest.fixture()
def fixture_funtion():
  print("START")
  yield
  print("FINISH")

class TestCases():
  def test_case1(self, fixture_funtion):
    print("Case1")

""" 
Result 
"""
# START
# Case1
# FINISH

2. addfinalizer

• Same as yield, but need to register teardown function.

import pytest

@pytest.fixture()
def fixture_funtion(request):
  print("START")
  
  def final_function():
    print("FINISH")

  request.addfinalizer(final_function)

class TestCases():
  def test_case1(self, fixture_funtion):
    print("Case1")

""" 
Result 
"""
# START
# Case1
# FINISH

Parametrizing

• If test cases need duplicate parameters, we can pass parameters through request.

import pytest

@pytest.fixture(params=[1, 2])
def fixture_funtion(request):
  print("START")
  yield request.param

class TestCases():
  def test_case1(self, fixture_funtion):
    print("Case1")
    print(fixture_funtion)

  def test_case2(self, fixture_funtion):
    print("Case2")
    print(fixture_funtion)

""" 
Result 
"""
# START
# Case1
# 1
# START
# Case1
# 2
# START
# Case2
# 1
# START
# Case2
# 2

Usage

1. Basic

import pytest

@pytest.fixture()
def init_funtion():
  print("INIT")

class TestCases():
  def test_case1(self, init_funtion):
    print("Case1")

2. Autouse

import pytest

@pytest.fixture(autouse=True)
def init_funtion():
  print("INIT")

class TestCases():
  def test_case1(self):
    print("Case1")

3. Pytest Mark

import pytest

@pytest.fixture()
def init_funtion():
  print("INIT")

@pytest.mark.usefixtures("init_funtion")
class TestCases():
  def test_case1(self):
    print("Case1")