第1章 快速入门

什么是pytest？

pytest是一个强大的Python测试工具，它可以用于所有类型和级别的软件测试。 Pytest可以被开发团队，QA团队，独立测试小组，实践TDD的个人和开放源代码项目。实际上，整个互联网上的项目都是从unittest或者nose转向pytest，包括Mozilla和Dropbox。为什么？因为pytest提供强大的功能，如'断言'重写，第三方插件模型，强大但简单的fixture模型。

pytest是软件测试框架, 也是命令行工具。它会自动找到你写的测试，运行测试并报告结果。可编写插件或安装第三方来扩展插件。它可以用来测试Python发行版。它很容易与其他工具对接，如持续集成和网页自动化。

Pytest脱颖而出的原因：

• 简单

• 易读

• 用assert来测试失败，而不是self.assertEqual() 或者self.assertLessThan()

• 可运行unittest或nose测试。

事实上很多自动化测试平台，底层就是用驱动的。它们用flask或django等提供友好的页面展示，但是核心层还是用pytest和一些测试库的开发。

本文基于　ubuntu 20，　python3.8书写，但是在其他平台通常也应该可以执行。

• 代码地址

安装

# pip install pytest
...

$ pytest -h # 查看帮助
usage: pytest [options] [file_or_dir] [file_or_dir] [...]

positional arguments:
  file_or_dir

general:
  -k EXPRESSION         only run tests which match the given substring expression. An expression is a python evaluatable expression
                        where all names are substring-matched against test names and their parent classes. Example: -k 'test_method
                        or test_other' matches all test functions and classes whose name contains 'test_method' or 'test_other',
                        while -k 'not test_method' matches those that don't contain 'test_method' in their names. -k 'not
                        test_method and not test_other' will eliminate the matches. Additionally keywords are matched to classes
                        and functions containing extra names in their 'extra_keyword_matches' set, as well as functions which have
                        names assigned directly to them. The matching is case-insensitive.
  -m MARKEXPR           only run tests matching given mark expression.
                        For example: -m 'mark1 and not mark2'.
  --markers             show markers (builtin, plugin and per-project ones).
  -x, --exitfirst       exit instantly on first error or failed test.
  --fixtures, --funcargs
                        show available fixtures, sorted by plugin appearance (fixtures with leading '_' are only shown with '-v')
  --fixtures-per-test   show fixtures per test
  --pdb                 start the interactive Python debugger on errors or KeyboardInterrupt.
  --pdbcls=modulename:classname
                        start a custom interactive Python debugger on errors. For example:
                        --pdbcls=IPython.terminal.debugger:TerminalPdb
  --trace               Immediately break when running each test.
  --capture=method      per-test capturing method: one of fd|sys|no|tee-sys.
  -s                    shortcut for --capture=no.
  --runxfail            report the results of xfail tests as if they were not marked
  --lf, --last-failed   rerun only the tests that failed at the last run (or all if none failed)
  --ff, --failed-first  run all tests, but run the last failures first.
                        This may re-order tests and thus lead to repeated fixture setup/teardown.
  --nf, --new-first     run tests from new files first, then the rest of the tests sorted by file mtime
  --cache-show=[CACHESHOW]
                        show cache contents, don't perform collection or tests. Optional argument: glob (default: '*').
  --cache-clear         remove all cache contents at start of test run.
  --lfnf={all,none}, --last-failed-no-failures={all,none}
                        which tests to run with no previously (known) failures.
  --sw, --stepwise      exit on test failure and continue from last failing test next time
  --stepwise-skip       ignore the first failing test but stop on the next failing test

reporting:
  --durations=N         show N slowest setup/test durations (N=0 for all).
  --durations-min=N     Minimal duration in seconds for inclusion in slowest list. Default 0.005
  -v, --verbose         increase verbosity.
  --no-header           disable header
  --no-summary          disable summary
  -q, --quiet           decrease verbosity.
  --verbosity=VERBOSE   set verbosity. Default is 0.
  -r chars              show extra test summary info as specified by chars: (f)ailed, (E)rror, (s)kipped, (x)failed, (X)passed,
                        (p)assed, (P)assed with output, (a)ll except passed (p/P), or (A)ll. (w)arnings are enabled by default (see
                        --disable-warnings), 'N' can be used to reset the list. (default: 'fE').
  --disable-warnings, --disable-pytest-warnings
                        disable warnings summary
  -l, --showlocals      show locals in tracebacks (disabled by default).
  --tb=style            traceback print mode (auto/long/short/line/native/no).
  --show-capture={no,stdout,stderr,log,all}
                        Controls how captured stdout/stderr/log is shown on failed tests. Default is 'all'.
  --full-trace          don't cut any tracebacks (default is to cut).
  --color=color         color terminal output (yes/no/auto).
  --code-highlight={yes,no}
                        Whether code should be highlighted (only if --color is also enabled)
  --pastebin=mode       send failed|all info to bpaste.net pastebin service.
  --junit-xml=path      create junit-xml style report file at given path.
  --junit-prefix=str    prepend prefix to classnames in junit-xml output

pytest-warnings:
  -W PYTHONWARNINGS, --pythonwarnings=PYTHONWARNINGS
                        set which warnings to report, see -W option of python itself.
  --maxfail=num         exit after first num failures or errors.
  --strict-config       any warnings encountered while parsing the `pytest` section of the configuration file raise errors.
  --strict-markers, --strict
                        markers not registered in the `markers` section of the configuration file raise errors.
  -c file               load configuration from `file` instead of trying to locate one of the implicit configuration files.
  --continue-on-collection-errors
                        Force test execution even if collection errors occur.
  --rootdir=ROOTDIR     Define root directory for tests. Can be relative path: 'root_dir', './root_dir', 'root_dir/another_dir/';
                        absolute path: '/home/user/root_dir'; path with variables: '$HOME/root_dir'.

collection:
  --collect-only, --co  only collect tests, don't execute them.
  --pyargs              try to interpret all arguments as python packages.
  --ignore=path         ignore path during collection (multi-allowed).
  --ignore-glob=path    ignore path pattern during collection (multi-allowed).
  --deselect=nodeid_prefix
                        deselect item (via node id prefix) during collection (multi-allowed).
  --confcutdir=dir      only load conftest.py's relative to specified dir.
  --noconftest          Don't load any conftest.py files.
  --keep-duplicates     Keep duplicate tests.
  --collect-in-virtualenv
                        Don't ignore tests in a local virtualenv directory
  --import-mode={prepend,append,importlib}
                        prepend/append to sys.path when importing test modules and conftest files, default is to prepend.
  --doctest-modules     run doctests in all .py modules
  --doctest-report={none,cdiff,ndiff,udiff,only_first_failure}
                        choose another output format for diffs on doctest failure
  --doctest-glob=pat    doctests file matching pattern, default: test*.txt
  --doctest-ignore-import-errors
                        ignore doctest ImportErrors
  --doctest-continue-on-failure
                        for a given doctest, continue to run after the first failure

test session debugging and configuration:
  --basetemp=dir        base temporary directory for this test run.(warning: this directory is removed if it exists)
  -V, --version         display pytest version and information about plugins.When given twice, also display information about
                        plugins.
  -h, --help            show help message and configuration info
  -p name               early-load given plugin module name or entry point (multi-allowed).
                        To avoid loading of plugins, use the `no:` prefix, e.g. `no:doctest`.
  --trace-config        trace considerations of conftest.py files.
  --debug               store internal tracing debug information in 'pytestdebug.log'.
  -o OVERRIDE_INI, --override-ini=OVERRIDE_INI
                        override ini option with "option=value" style, e.g. `-o xfail_strict=True -o cache_dir=cache`.
  --assert=MODE         Control assertion debugging tools.
                        'plain' performs no assertion debugging.
                        'rewrite' (the default) rewrites assert statements in test modules on import to provide assert expression
                        information.
  --setup-only          only setup fixtures, do not execute tests.
  --setup-show          show setup of fixtures while executing tests.
  --setup-plan          show what fixtures and tests would be executed but don't execute anything.

logging:
  --log-level=LEVEL     level of messages to catch/display.
                        Not set by default, so it depends on the root/parent log handler's effective level, where it is "WARNING"
                        by default.
  --log-format=LOG_FORMAT
                        log format as used by the logging module.
  --log-date-format=LOG_DATE_FORMAT
                        log date format as used by the logging module.
  --log-cli-level=LOG_CLI_LEVEL
                        cli logging level.
  --log-cli-format=LOG_CLI_FORMAT
                        log format as used by the logging module.
  --log-cli-date-format=LOG_CLI_DATE_FORMAT
                        log date format as used by the logging module.
  --log-file=LOG_FILE   path to a file when logging will be written to.
  --log-file-level=LOG_FILE_LEVEL
                        log file logging level.
  --log-file-format=LOG_FILE_FORMAT
                        log format as used by the logging module.
  --log-file-date-format=LOG_FILE_DATE_FORMAT
                        log date format as used by the logging module.
  --log-auto-indent=LOG_AUTO_INDENT
                        Auto-indent multiline messages passed to the logging module. Accepts true|on, false|off or an integer.

[pytest] ini-options in the first pytest.ini|tox.ini|setup.cfg file found:

  markers (linelist):   markers for test functions
  empty_parameter_set_mark (string):
                        default marker for empty parametersets
  norecursedirs (args): directory patterns to avoid for recursion
  testpaths (args):     directories to search for tests when no files or directories are given in the command line.
  filterwarnings (linelist):
                        Each line specifies a pattern for warnings.filterwarnings. Processed after -W/--pythonwarnings.
  usefixtures (args):   list of default fixtures to be used with this project
  python_files (args):  glob-style file patterns for Python test module discovery
  python_classes (args):
                        prefixes or glob names for Python test class discovery
  python_functions (args):
                        prefixes or glob names for Python test function and method discovery
  disable_test_id_escaping_and_forfeit_all_rights_to_community_support (bool):
                        disable string escape non-ascii characters, might cause unwanted side effects(use at your own risk)
  console_output_style (string):
                        console output: "classic", or with additional progress information ("progress" (percentage) | "count").
  xfail_strict (bool):  default for the strict parameter of xfail markers when not given explicitly (default: False)
  enable_assertion_pass_hook (bool):
                        Enables the pytest_assertion_pass hook.Make sure to delete any previously generated pyc cache files.
  junit_suite_name (string):
                        Test suite name for JUnit report
  junit_logging (string):
                        Write captured log messages to JUnit report: one of no|log|system-out|system-err|out-err|all
  junit_log_passing_tests (bool):
                        Capture log information for passing tests to JUnit report:
  junit_duration_report (string):
                        Duration time to report: one of total|call
  junit_family (string):
                        Emit XML for schema: one of legacy|xunit1|xunit2
  doctest_optionflags (args):
                        option flags for doctests
  doctest_encoding (string):
                        encoding used for doctest files
  cache_dir (string):   cache directory path.
  log_level (string):   default value for --log-level
  log_format (string):  default value for --log-format
  log_date_format (string):
                        default value for --log-date-format
  log_cli (bool):       enable log display during test run (also known as "live logging").
  log_cli_level (string):
                        default value for --log-cli-level
  log_cli_format (string):
                        default value for --log-cli-format
  log_cli_date_format (string):
                        default value for --log-cli-date-format
  log_file (string):    default value for --log-file
  log_file_level (string):
                        default value for --log-file-level
  log_file_format (string):
                        default value for --log-file-format
  log_file_date_format (string):
                        default value for --log-file-date-format
  log_auto_indent (string):
                        default value for --log-auto-indent
  faulthandler_timeout (string):
                        Dump the traceback of all threads if a test takes more than TIMEOUT seconds to finish.
  addopts (args):       extra command line options
  minversion (string):  minimally required pytest version
  required_plugins (args):
                        plugins that must be present for pytest to run

environment variables:
  PYTEST_ADDOPTS           extra command line options
  PYTEST_PLUGINS           comma-separated plugins to load during startup
  PYTEST_DISABLE_PLUGIN_AUTOLOAD set to disable plugin auto-loading
  PYTEST_DEBUG             set to enable debug tracing of pytest's internals


to see available markers type: pytest --markers
to see available fixtures type: pytest --fixtures
(shown according to specified file_or_dir or current dir if not specified; fixtures with leading '_' are only shown with the '-v' option

快速入门

def test_passing():
    assert (1, 2, 3) == (1, 2, 3)

执行：

$ pytest pass_test.py 
======================================================= test session starts =======================================================
platform linux -- Python 3.8.3, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/andrew/code/python-api-tesing/python3_libraries/pytest_testing/ch1
collected 1 item                                                                                                                  

pass_test.py .                                                                                                              [100%]

======================================================== 1 passed in 0.04s ========================================================

pass_test.py后的点表示一个测试运行并通过。 如果你需要更多信息，您可以使用-v或--verbose

在彩色终端，PASSED和底线是绿色的。

def test_failing():
    assert (1, 2, 3) == (3, 2, 1)

执行：

如果没有参数，pytest会查看当前目录和所有子目录的测试文件(test_开头或者_test结尾)并运行。 也可以指定文件名，目录名称或这些名称的列表。

我们创建tasks的子目录，增加几个测试

task1_test.py

from collections import namedtuple

Task = namedtuple('Task', ['summary', 'owner', 'done', 'id'])
Task.__new__.__defaults__ = (None, None, False, None)


def test_defaults():
    """Using no parameters should invoke defaults."""
    t1 = Task()
    t2 = Task(None, None, False, None)
    assert t1 == t2


def test_member_access():
    """Check .field functionality of namedtuple."""
    t = Task('buy milk', 'brian')
    assert t.summary == 'buy milk'
    assert t.owner == 'brian'
    assert (t.done, t.id) == (False, None)

task2_test.py

from collections import namedtuple


Task = namedtuple('Task', ['summary', 'owner', 'done', 'id'])
Task.__new__.__defaults__ = (None, None, False, None)


def test_asdict():
    """_asdict() should return a dictionary."""
    t_task = Task('do something', 'okken', True, 21)
    t_dict = t_task._asdict()
    expected = {'summary': 'do something',
                'owner': 'okken',
                'done': True,
                'id': 21}
    assert t_dict == expected


def test_replace():
    """replace() should change passed in fields."""
    t_before = Task('finish book', 'brian', False)
    t_after = t_before._replace(id=10, done=True)
    t_expected = Task('finish book', 'brian', True, 10)
    assert t_after == t_expected

执行示例：

andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                         

fail_test.py F                                                                                      [ 16%]
pass_test.py .                                                                                      [ 33%]
tasks/task1_test.py ..                                                                              [ 66%]
tasks/task2_test.py ..                                                                              [100%]

================================================ FAILURES =================================================
______________________________________________ test_failing _______________________________________________

    def test_failing():
>       assert (1, 2, 3) == (3, 2, 1)
E       assert (1, 2, 3) == (3, 2, 1)
E         At index 0 diff: 1 != 3
E         Use -v to get the full diff

fail_test.py:2: AssertionError
=================================== 1 failed, 5 passed in 0.04 seconds ====================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                         

tasks/task1_test.py ..                                                                              [ 50%]
tasks/task2_test.py ..                                                                              [100%]

======================================== 4 passed in 0.02 seconds =========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest -v tasks/task2_test.py::test_asdict
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0 -- /usr/bin/python3
cachedir: .pytest_cache
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 1 item                                                                                          

tasks/task2_test.py::test_asdict PASSED                                                             [100%]

======================================== 1 passed in 0.01 seconds =========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest --collect-only
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                         
<Module 'fail_test.py'>
  <Function 'test_failing'>
<Module 'pass_test.py'>
  <Function 'test_passing'>
<Module 'tasks/task1_test.py'>
  <Function 'test_defaults'>
  <Function 'test_member_access'>
<Module 'tasks/task2_test.py'>
  <Function 'test_asdict'>
  <Function 'test_replace'>

====================================== no tests ran in 0.02 seconds =======================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest --collect-only -k "asdict or defaults"
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items / 4 deselected                                                                          
<Module 'tasks/task1_test.py'>
  <Function 'test_defaults'>
<Module 'tasks/task2_test.py'>
  <Function 'test_asdict'>

====================================== 4 deselected in 0.02 seconds =======================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest -k "asdict or defaults"
=========================================== test session starts ===========================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items / 4 deselected                                                                          

tasks/task1_test.py .                                                                               [ 50%]
tasks/task2_test.py .                                                                               [100%]

================================= 2 passed, 4 deselected in 0.02 seconds ==================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

发现规则小结

• 测试文件应该命名为test_<something>.py或<something>_test.py
• 测试方法和函数应该被命名为test_<something>。
• 测试类应该被命名为Test<Something>

结果类型：

以下是测试功能的可能结果：

• PASSED (.)：测试成功。
• FAILED (F):测试失败(或XPASS + strict)。
• SKIPPED (s): 测试被跳过。 你可以使用@pytest.mark.skip()或 pytest.mark.skipif()修饰器告诉pytest跳过测试
• xfail (x)：预期测试失败。@pytest.mark.xfail()
• XPASS (X)：测试不应该通过。
• ERROR (E)：错误

更多选项

• marker 标签

比如只执行test_replace()和test_member_access()

import pytest
...
@pytest.mark.run_these_please
def test_member_access():
...

执行

$  cd  /path/to/code/ch1/tasks
 pytest  -v  -m  run_these_please
$
================== test session starts ===================
collected 4 items
task2.py::test_replace PASSED
task1.py::test_member_access PASSED
=================== 2 tests deselected ===================
========= 2 passed, 2 deselected in 0.02 seconds =========

更多执行方法：-m "mark1 and mark2"、 -m "mark1 and not mark2"、-m "mark1 or mark2"

• -x, –exitfirst 失败后停止执行

  首次失败后停止执行：py.test -x

  py.test --maxfail=2 两次失败之后停止执行

$ pytest -x
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                                     

fail_test.py F

====================================================== FAILURES =======================================================
____________________________________________________ test_failing _____________________________________________________

    def test_failing():
>       assert (1, 2, 3) == (3, 2, 1)
E       assert (1, 2, 3) == (3, 2, 1)
E         At index 0 diff: 1 != 3
E         Use -v to get the full diff

fail_test.py:2: AssertionError
============================================== 1 failed in 0.04 seconds ===============================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

1$ pytest --tb=no
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                                     

fail_test.py F                                                                                                  [ 16%]
pass_test.py .                                                                                                  [ 33%]
tasks/task1_test.py ..                                                                                          [ 66%]
tasks/task2_test.py ..                                                                                          [100%]

========================================= 1 failed, 5 passed in 0.05 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

$ pytest --maxfail=1 --tb=no
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                                     

fail_test.py F

============================================== 1 failed in 0.04 seconds ===============================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest --maxfail=2  --tb=no
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                                     

fail_test.py F                                                                                                  [ 16%]
pass_test.py .                                                                                                  [ 33%]
tasks/task1_test.py ..                                                                                          [ 66%]
tasks/task2_test.py ..                                                                                          [100%]

========================================= 1 failed, 5 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

• 设置捕捉

默认捕捉方式为file descriptor (FD)级捕捉。捕捉所有到操作系统的1,2输出。

syslevel级捕捉只捕捉python的sys.stdout和sys.stderr。

py.test -s            # disable all capturing 实际为--capture=no这样print就可以在屏幕输出。
py.test --capture=sys # replace sys.stdout/stderr with in-mem files
py.test --capture=fd  # also point filedescriptors 1 and 2 to temp file

• --lf, --last-failed 执行上次失败的测试

多在--tb 之后使用

--ff / --failed-first则会先执行失败的，然后执行成功的。

$ pytest --lf
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items / 5 deselected                                                                                      
run-last-failure: rerun previous 1 failure

fail_test.py F                                                                                                  [100%]

====================================================== FAILURES =======================================================
____________________________________________________ test_failing _____________________________________________________

    def test_failing():
>       assert (1, 2, 3) == (3, 2, 1)
E       assert (1, 2, 3) == (3, 2, 1)
E         At index 0 diff: 1 != 3
E         Use -v to get the full diff

fail_test.py:2: AssertionError
======================================= 1 failed, 5 deselected in 0.04 seconds ========================================
$ pytest --ff --tb=no
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 6 items                                                                                                     
run-last-failure: rerun previous 1 failure first

fail_test.py F                                                                                                  [ 16%]
pass_test.py .                                                                                                  [ 33%]
tasks/task1_test.py ..                                                                                          [ 66%]
tasks/task2_test.py ..                                                                                          [100%]

========================================= 1 failed, 5 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

• -q 静默模式

-q, --quiet decrease verbosity.

$ pytest -q
F.....                                                                                                          [100%]
====================================================== FAILURES =======================================================
____________________________________________________ test_failing _____________________________________________________

    def test_failing():
>       assert (1, 2, 3) == (3, 2, 1)
E       assert (1, 2, 3) == (3, 2, 1)
E         At index 0 diff: 1 != 3
E         Full diff:
E         - (1, 2, 3)
E         ?  ^     ^
E         + (3, 2, 1)
E         ?  ^     ^

fail_test.py:2: AssertionError
1 failed, 5 passed in 0.04 seconds
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest -qq
F.....                                                                                                          [100%]
====================================================== FAILURES =======================================================
____________________________________________________ test_failing _____________________________________________________

    def test_failing():
>       assert (1, 2, 3) == (3, 2, 1)
E       assert (1, 2, 3) == (3, 2, 1)
E         At index 0 diff: 1 != 3
E         Full diff:
E         - (1, 2, 3)
E         ?  ^     ^
E         + (3, 2, 1)
E         ?  ^     ^

fail_test.py:2: AssertionError

• -l 在traceback中显示本地变量

--showlocals 在traceback中显示本地变量

修改test_replace()中的t_expected = Task( 'finish book' , 'brian' , True, 10)为t_expected = Task( 'finish book' , 'brian' , True, 11)

py.test --showlocals 在traceback中显示本地变量
py.test -l 在traceback中显示本地变量（快捷方式）

$ pytest tasks
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py .F                                                                                          [100%]

====================================================== FAILURES =======================================================
____________________________________________________ test_replace _____________________________________________________

    def test_replace():
        """replace() should change passed in fields."""
        t_before = Task('finish book', 'brian', False)
        t_after = t_before._replace(id=10, done=True)
        t_expected = Task('finish book', 'brian', True, 11)
>       assert t_after == t_expected
E       AssertionError: assert Task(summary=...e=True, id=10) == Task(summary='...e=True, id=11)
E         At index 3 diff: 10 != 11
E         Use -v to get the full diff

tasks/task2_test.py:26: AssertionError
========================================= 1 failed, 3 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks -l
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py .F                                                                                          [100%]

====================================================== FAILURES =======================================================
____________________________________________________ test_replace _____________________________________________________

    def test_replace():
        """replace() should change passed in fields."""
        t_before = Task('finish book', 'brian', False)
        t_after = t_before._replace(id=10, done=True)
        t_expected = Task('finish book', 'brian', True, 11)
>       assert t_after == t_expected
E       AssertionError: assert Task(summary=...e=True, id=10) == Task(summary='...e=True, id=11)
E         At index 3 diff: 10 != 11
E         Use -v to get the full diff

t_after    = Task(summary='finish book', owner='brian', done=True, id=10)
t_before   = Task(summary='finish book', owner='brian', done=False, id=None)
t_expected = Task(summary='finish book', owner='brian', done=True, id=11)

tasks/task2_test.py:26: AssertionError
========================================= 1 failed, 3 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

• –tb=style

py.test -l 在traceback中显示本地变量（快捷方式）
py.test --tb=auto 默认格式，首尾为long，其他为short
py.test --tb=long 详细的traceback信息格式化形式
py.test --tb=native 标准库格式化形式, 没有额外信息
py.test --tb=short 更短的traceback格式
py.test --tb=line 每个错误一行
py.test --tb=no 无traceback
py.test --full-trace 最详细的格式

实例：

$ pytest tasks --tb no
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py .F                                                                                          [100%]

========================================= 1 failed, 3 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks --tb line
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py .F                                                                                          [100%]

====================================================== FAILURES =======================================================
/home/andrew/code/backup/pytest_testing/ch1/tasks/task2_test.py:26: AssertionError: assert Task(summary=...e=True, id=10) == Task(summary='...e=True, id=11)
========================================= 1 failed, 3 passed in 0.03 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks --tb short
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py .F                                                                                          [100%]

====================================================== FAILURES =======================================================
____________________________________________________ test_replace _____________________________________________________
tasks/task2_test.py:26: in test_replace
    assert t_after == t_expected
E   AssertionError: assert Task(summary=...e=True, id=10) == Task(summary='...e=True, id=11)
E     At index 3 diff: 10 != 11
E     Use -v to get the full diff
========================================= 1 failed, 3 passed in 0.04 seconds ==========================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ vi tasks/task2_test.py 
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks  --duration=3
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py ..                                                                                          [100%]

============================================== slowest 3 test durations ===============================================
0.00s setup    tasks/task1_test.py::test_defaults
0.00s setup    tasks/task2_test.py::test_asdict
0.00s setup    tasks/task2_test.py::test_replace
============================================== 4 passed in 0.02 seconds ===============================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$

• –durations=N

统计最慢执行时间

andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ pytest tasks  --duration=3
================================================= test session starts =================================================
platform linux -- Python 3.5.2, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
rootdir: /home/andrew/code/backup/pytest_testing/ch1, inifile:
collected 4 items                                                                                                     

tasks/task1_test.py ..                                                                                          [ 50%]
tasks/task2_test.py ..                                                                                          [100%]

============================================== slowest 3 test durations ===============================================
0.00s setup    tasks/task1_test.py::test_defaults
0.00s setup    tasks/task2_test.py::test_asdict
0.00s setup    tasks/task2_test.py::test_replace
============================================== 4 passed in 0.02 seconds ===============================================
andrew@andrew-PowerEdge-T630:~/code/backup/pytest_testing/ch1$ 

参考资料

• 本文涉及的python测试开发库 谢谢点赞！
• 本文相关书籍下载
• 代码地址