byexample

Write snippets of code in your documentation and execute them as regression tests.

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Options

You can control certain behaviours of the examples through a set of options.

If the option is set per example using byexample: <opt>, it will affect only that example.

>>> list(range(10))             # byexample: +norm-ws
[0,  1,  2,  3,  4,
 5,  6,  7,  8,  9]

If the option is set in the command line using -o <opt>, it will affect all the examples.

$ byexample -l python -o "+norm-ws" test/ds/python-tutorial.v2.md
<...>
File test/ds/python-tutorial.v2.md, 4/4 test ran in <...> seconds
[PASS] Pass: 4 Fail: 0 Skip: 0

If the option begins with -, byexample may get confuse and it will complain that no argument was given to --options:

$ byexample -l python -o -warn-tab test/ds/example-with-tabs-in-code.md
<...>
byexample: error: argument -o/--options: expected one argument
If you wrote --options -foo, try put an equal like --options=-foo
and use quotes if you want to set multiples options like --options='-foo +bar'

The error is because byexample presumes that -warn-tab is another command line flag like -l and -o and not the argument for -o.

As the error message suggests you can workaround this joining -o with its argument with an =:

$ byexample -l python -o=-warn-tab test/ds/example-with-tabs-in-code.md
<...>
File test/ds/example-with-tabs-in-code.md, <...>
[PASS] Pass: 1 Fail: 0 Skip: 0

If you need to pass multiple options to -o you can quote them together:

$ byexample -l python -o='-warn-tab +norm-ws' test/ds/example-with-tabs-in-code.md
<...>
File test/ds/example-with-tabs-in-code.md, <...>
[PASS] Pass: 1 Fail: 0 Skip: 0

Show all the options

You can know what options are available for a given language running the help integrated in byexample.

For Python you could do:

$ byexample -l python --show-options
byexample's options
-------------------
<...>:
  +fail-fast            if an example fails, fail and stop all the execution.
  +norm-ws              ignore the amount of whitespaces.
  <...>
python's specific options
-------------------------
<...>
  +py-doctest           enable the compatibility with doctest.
  +py-pretty-print      enable the pretty print enhancement.
  <...>

There is a set of common options supplied by byexample and can be used in any example.

Other languages and concerns may add their owns.

Loading options from a file

If the amount of options is a little overwhelming for you, you can write them down to a file and let byexample load them for you.

The only convention that you need to follow is to write one option per line. If the option receives one argument you can separate them by = or by a space but if there is more than one argument you will have to write the option and the arguments one by one in its own line.

$ cat test/ds/options_file
# Options and their arguments are separated by a = or by a space
-l python
--options=+norm-ws
<...>
# But if the option receives more than one argument, all of them
# must be in its own line
--skip
test/ds/pkg/foo1.py
test/ds/pkg/foo2.py
<...>
# This wouldn't work:
#--skip test/ds/pkg/foo1.py test/ds/pkg/foo2.py
<...>

Then load it with @ and the file; you can use multiple files and combine them with more options from the command line:

$ byexample @test/ds/options_file -- test/ds/python-tutorial.v2.md
<...>
File test/ds/python-tutorial.v2.md, 4/4 test ran in <...> seconds
[PASS] Pass: 4 Fail: 0 Skip: 0

Note: before 10.5.2 the options in the file required to be followed by an = like -l=python; spaces were not allowed.

File pattern expansions

Consider the following:

$ byexample -l python test/ds/pkg/*.py | grep pkg | sort    # byexample: +timeout=8
File test/ds/pkg/bar1.py, 1/1 test ran in <...> seconds
File test/ds/pkg/foo1.py, 1/1 test ran in <...> seconds
File test/ds/pkg/foo2.py, 1/1 test ran in <...> seconds

Your shell usually expands test/ds/pkg/*.py into a list of files: test/ds/pkg/bar1.py, test/ds/pkg/foo1.py and test/ds/pkg/foo2.py

The same happens with the argument list for --skip, it is expanded by your shell.

$ byexample -l python --skip test/ds/pkg/foo* -- test/ds/pkg/*.py | grep pkg | sort    # byexample: +timeout=8
File test/ds/pkg/bar1.py, 1/1 test ran in <...> seconds

Since 10.0.3, byexample does the same glob expansion even if you shell does not. This is in particular useful if the list of files is in a file (where your shell never ever see).

$ cat test/ds/pkg/bopts
--skip=test/ds/pkg/foo*.py
--
test/ds/pkg/*.py

$ byexample -l python @test/ds/pkg/bopts | grep pkg | sort    # byexample: +timeout=8
File test/ds/pkg/bar1.py, 1/1 test ran in <...> seconds

Since 11.0.0, byexample also does the so called brace expansion:

$ cat test/ds/pkg/bopts-brace
--skip=test/ds/pkg/foo{1..2}.py
--
test/ds/pkg/*.{py,md}

$ byexample -l python @test/ds/pkg/bopts-brace | grep pkg | sort    # byexample: +timeout=8
File test/ds/pkg/bar1.py, 1/1 test ran in <...> seconds
File test/ds/pkg/zaz.md, 1/1 test ran in <...> seconds

Arguments per environment

If you run you tests under different environments and you need to pass different options in each one, you may benefit of writing a single argument file to work as a template and use a template engine like Jinja2 to generate different argument files based on the environment.

This is probably a real exotic super-advanced use of byexample but it may save you some typing! Check the recipe for a full example.