coverage代码覆盖率测试介绍

背景知识补充

1、什么是覆盖率

测试过程中提到的覆盖率，指的是已测试的内容，占待测内容的百分比，在一定程度上反应测试的完整程度。

覆盖率有可以根据要衡量的对象细分很多种，比如接口覆盖率、分支覆盖率、行覆盖率等等

2、做覆盖率有什么用处

覆盖率的好处是可以将测试的完整性量化，可以作为补充测试的手段，也可以在一定程度上佐证测试结果的可靠性。

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简介

代码覆盖率测量通常用于衡量测试的有效性。它可以显示你的代码的哪些部分正在被测试执行，哪些没有被执行。

coverage是一个测量 Python 程序代码覆盖率的工具。它监视你的程序，并分析源码生成代码覆盖率报告。

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安装

coverage依赖python环境

python环境安装：https://computingforgeeks.com/install-latest-python-on-centos-linux/

安装coverage

python3 -m pip install coverage
or
pip3 install coverage

安装完成

coverage --version
Coverage.py, version 7.2.5 with C extension
Full documentation is at https://coverage.readthedocs.io/en/7.2.5

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命令概览

coverage支持命令如下

[yhgao@localhost ~]$ coverage --help
Coverage.py, version 7.2.5 with C extension
Measure, collect, and report on code coverage in Python programs.usage: coverage <command> [options] [args]Commands:annotate    Annotate source files with execution information.combine     Combine a number of data files.debug       Display information about the internals of coverage.pyerase       Erase previously collected coverage data.help        Get help on using coverage.py.html        Create an HTML report.json        Create a JSON report of coverage results.lcov        Create an LCOV report of coverage results.report      Report coverage stats on modules.run         Run a Python program and measure code execution.xml         Create an XML report of coverage results.Use "coverage help <command>" for detailed help on any command.
Full documentation is at https://coverage.readthedocs.io/en/7.2.5

其中每个小命令后面可以查看更详细的帮助， 以run命令举例

[yhgao@localhost ~]$ coverage run --help
Usage: coverage run [options] <pyfile> [program options]Run a Python program, measuring code execution.Options:-a, --append          Append coverage data to .coverage, otherwise it startsclean each time.--branch              Measure branch coverage in addition to statementcoverage.--concurrency=LIBS    Properly measure code using a concurrency library.Valid values are: eventlet, gevent, greenlet,multiprocessing, thread, or a comma-list of them.--context=LABEL       The context label to record for this coverage run.--data-file=OUTFILE   Write the recorded coverage data to this file.Defaults to '.coverage'. [env: COVERAGE_FILE]--include=PAT1,PAT2,...Include only files whose paths match one of thesepatterns. Accepts shell-style wildcards, which must bequoted.-m, --module          <pyfile> is an importable Python module, not a scriptpath, to be run as 'python -m' would run it.--omit=PAT1,PAT2,...  Omit files whose paths match one of these patterns.Accepts shell-style wildcards, which must be quoted.-L, --pylib           Measure coverage even inside the Python installedlibrary, which isn't done by default.-p, --parallel-mode   Append the machine name, process id and random numberto the data file name to simplify collecting data frommany processes.--source=SRC1,SRC2,...A list of directories or importable names of code tomeasure.--timid               Use a simpler but slower trace method. Try this if youget seemingly impossible results!--debug=OPTS          Debug options, separated by commas. [env:COVERAGE_DEBUG]-h, --help            Get help on this command.--rcfile=RCFILE       Specify configuration file. By default '.coveragerc','setup.cfg', 'tox.ini', and 'pyproject.toml' aretried. [env: COVERAGE_RCFILE]Full documentation is at https://coverage.readthedocs.io/en/7.2.5

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快速使用

如果你的测试运行程序命令以“python”开头，只需将初始的“python”替换为“coverage run”即可。

python something.py -->> becomes -->> coverage run something.pypython -m amodule -->> becomes -->> coverage run -m amodule

python其他单元测试框架

pytest
pytest arg1 arg2 arg3 -->> becomes -->> coverage run -m pytest arg1 arg2 arg3unittest
python -m unittest discover -->> becomes -->>  coverage run -m unittest discovernosetest
nosetests arg1 arg2 -->> becomes -->> coverage run -m nose arg1 arg2

测试完成后会在当前目录下默认生成一个.coverage文件，这里面保存了代码覆盖率结果，也可以通过–data-file生成指定名称的文件

直接查看

coverage report

$ coverage report -m
Name                      Stmts   Miss  Cover   Missing
-------------------------------------------------------
my_program.py                20      4    80%   33-35, 39
my_other_module.py           56      6    89%   17-23
-------------------------------------------------------
TOTAL                        76     10    87%

其他查看方式

使用其他格式查看，例如html，会生成html文件，使用浏览器打开index.html即可查看

coverage html[yhgao@localhost coverage]$ coverage html
Wrote HTML report to htmlcov/index.html
[yhgao@localhost coverage]$ ll
总用量 4
-rw-rw-r-- 1 yhgao yhgao 679 6月  15 16:49 demo.py
drwxrwxr-x 2 yhgao yhgao 190 6月  15 16:51 htmlcov[yhgao@localhost coverage]$ cd htmlcov/
[yhgao@localhost htmlcov]$ ls -al
总用量 92
drwxrwxr-x 2 yhgao yhgao   190 6月  15 16:51 .
drwxrwxr-x 3 yhgao yhgao    53 6月  15 16:51 ..
-rw-rw-r-- 1 yhgao yhgao 21359 6月  15 16:51 coverage_html.js
-rw-rw-r-- 1 yhgao yhgao 11790 6月  15 16:51 demo_py.html
-rw-rw-r-- 1 yhgao yhgao  1732 6月  15 16:51 favicon_32.png
-rw-rw-r-- 1 yhgao yhgao    27 6月  15 16:51 .gitignore
-rw-rw-r-- 1 yhgao yhgao  3816 6月  15 16:51 index.html  //浏览器打开该文件
-rw-rw-r-- 1 yhgao yhgao  9004 6月  15 16:51 keybd_closed.png
-rw-rw-r-- 1 yhgao yhgao  9003 6月  15 16:51 keybd_open.png
-rw-rw-r-- 1 yhgao yhgao   236 6月  15 16:51 status.json
-rw-rw-r-- 1 yhgao yhgao 12387 6月  15 16:51 style.css

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Demo

下面以一个demo.py举例

测试目标（%）：100

测试case数量（个）：3

//查看demo文件
[yhgao@bogon coverage]$ cat demo.py
import sysnum = int(sys.argv[1])
if num == 1:print('output num: 1')
else:if num == 2:print('output num: 2')elif (num > 2 or num < 1):print('error input num')//python执行结果
[yhgao@bogon coverage]$ python demo.py 1
output num: 1
[yhgao@bogon coverage]$ python demo.py 2
output num: 2
[yhgao@bogon coverage]$ python demo.py 3
error input num//coverage执行代码覆盖率（区分单个case情况）
[yhgao@bogon coverage]$ coverage run --data-file=c1 demo.py 1
output num: 1
[yhgao@bogon coverage]$ coverage run --data-file=c2 demo.py 2
output num: 2
[yhgao@bogon coverage]$ coverage run --data-file=c3 demo.py 3
error input num//查看每个代码覆盖率文件
[yhgao@bogon coverage]$ coverage report --data-file=c1
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      4    50%
-----------------------------
TOTAL         8      4    50%
[yhgao@bogon coverage]$ coverage report --data-file=c2
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      3    62%
-----------------------------
TOTAL         8      3    62%
[yhgao@bogon coverage]$ coverage report --data-file=c3
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      2    75%
-----------------------------
TOTAL         8      2    75%//合并代码覆盖率文件
[yhgao@bogon coverage]$ coverage combine --data-file=cc c1 c2 c3
Combined data file c1
Combined data file c2
Combined data file c3//查看合并后的代码覆盖率文件
[yhgao@bogon coverage]$ coverage report --data-file=cc
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      0   100%
-----------------------------
TOTAL         8      0   100%可以看到整合之后的代码覆盖率达到100%，我们也就可以据此判断我们的3个测试case是符合要求的。//coverage执行代码覆盖率（不区分单个case情况）
未指定-a的情况：
[yhgao@bogon coverage]$ coverage run --data-file=cc2 demo.py 1
output num: 1
[yhgao@bogon coverage]$ coverage run --data-file=cc2 demo.py 2
output num: 2
[yhgao@bogon coverage]$ coverage run --data-file=cc2 demo.py 3
error input num
[yhgao@bogon coverage]$ coverage report --data-file=cc2
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      2    75%
-----------------------------
TOTAL         8      2    75%代码覆盖率是会被覆盖的，所以只保留最后一个case的代码覆盖率指定-a的情况：
[yhgao@bogon coverage]$ coverage run -a --data-file=cc2 demo.py 1
output num: 1
[yhgao@bogon coverage]$ coverage run -a --data-file=cc2 demo.py 2
output num: 2
[yhgao@bogon coverage]$ coverage run -a --data-file=cc2 demo.py 3
error input num
[yhgao@bogon coverage]$ coverage report --data-file=cc2
Name      Stmts   Miss  Cover
-----------------------------
demo.py       8      0   100%
-----------------------------
TOTAL         8      0   100%指定-a和同一个data-file即可不用执行coverage combine，直接得到一份儿完整的代码覆盖率文件