Pytest authoritative guide -01 Installation and Getting Started

Installation and Getting Started

Support Python version : Python 2.6,2.7,3.3,3.4,3.5, Jython, PyPy- 2.3

Supported platforms : Unix / Posix and Windows

PyPI package name : pytest

Dependency : py, colorama (Windows)

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Pytest the creation is a simple and scalable test case has become very convenient framework. Test case is clear, easy to read without a lot of complicated code. Just a few minutes you can expand a small unit test your application or library or complex functional tests.

Installation Pytest

Execute the following command at the command line

pip install -U pytest

Check that the installed version Pytest

$ pytest --version
This is pytest version 3.x.y,imported from $PYTHON_PREFIX/lib/python3.6/site-packages/pytest.py

Creating your first test case

Only four lines of code to create a simple test:

# test_sample.py文件内容
def func(x):
    return x + 1

def test_answer():
    assert func(3) == 5

It's that simple. Now you can perform about this test case:

$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y,pytest-3.x.y,py-1.x.y,pluggy-0.x.y
rootdir: $REGENDOC_TMPDIR,inifile:
collected 1 item

test_sample.py F                                                     [100%]

================================= FAILURES =================================
_______________________________ test_answer ________________________________

    def test_answer():
>       assert func(3) == 5
E       assert 4 == 5
E        +  where 4 = func(3)

test_sample.py:5: AssertionError
========================= 1 failed in 0.12 seconds =========================

Because func(3)it does not mean 5that this test result information returned a failure.

Note:
You can use the assertstatement to assert expected results of your test cases. Senior assertion introspection Pytest can intelligently display intermediate results assertion expression, to avoid the variable name comes from the method in JUnit repeat the question.

The implementation of a number of test cases

pytestCommand execution of the current directory and all subdirectories test_*.pyand *_test.pyfile formats. In general, use cases need to follow standard test discovery rules.

Assertion throws an exception specified

Use raiseexception may be thrown in the corresponding code specified:

# test_sysexit.py文件内容
import pytest
def f():
    raise SystemExit(1)

def test_mytest():
    with pytest.raises(SystemExit):
        f()

Use "silent" mode, perform this test, such as:

$ pytest -q test_sysexit.py
.                                                                   [100%]
1 passed in 0.12 seconds

Class organizations use multiple test cases

Once you need to develop a number of test cases, you might want to use the class to organize them. Use Pytest can easily create a test class that contains multiple use cases:

# test_class.py文件内容
class TestClass(object):
    def test_one(self):
        x = "this"
        assert 'h' in x

    def test_two(self):
        x = "hello"
        assert hasattr(x,'check')

PytestPython can be found in all test cases found in use cases follow the agreed rules, so it can be found Testoutside at the beginning of the test class to class and all test_functions and methods beginning. Test category no longer inherit any object. We simply need to run this module to the file name.

$ pytest -q test_class.py
.F                                                                   [100%]
================================= FAILURES =================================
____________________________ TestClass.test_two ____________________________

self = <test_class.TestClass object at 0xdeadbeef>

    def test_two(self):
        x = "hello"
>       assert hasattr(x,'check')
E       AssertionError: assert False
E        +  where False = hasattr('hello','check')

test_class.py:8: AssertionError
1 failed,1 passed in 0.12 seconds

The first use case is executed successfully, the next day failed to execute use cases. You can easily understand the cause of the failure to intermediate values of assertions by variables.

Function test request to use a separate temporary directory

PytestIt provides built-in fixtures method parameters to use any resource, such as a separate temporary directory:

# test_tmpdir.py文件内容
def test_needsfiles(tmpdir):
    print (tmpdir)
    assert 0

Use the test function tmpdiras a parameter, Pytest to find and call the fixture factory method to create the appropriate resources before the test case function call. Prior to the test run, Pytest create a separate temporary directory for each test case:

$ pytest -q test_tmpdir.py
F                                                                    [100%]
================================= FAILURES =================================
_____________________________ test_needsfiles ______________________________

tmpdir = local('PYTEST_TMPDIR/test_needsfiles0')

    def test_needsfiles(tmpdir):
        print (tmpdir)
>       assert 0
E       assert 0

test_tmpdir.py:3: AssertionError
--------------------------- Captured stdout call ---------------------------
PYTEST_TMPDIR/test_needsfiles0
1 failed in 0.12 seconds

For more information about tmpdir process, see: temporary directories and files