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

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Environment Variables

byexample passes the environment variables to the interpreters and they are available from the examples and modules.

This is the default and quite handy if you want to make your documentation configurable for scripting.

Let’s say you have a shell example:

$ if [ "$PWD" != "/root" ]; then
>   echo "You must run this script from /root"
> fi
You must run this script from /root

Pasting a captured environment variable

But what if we want to capture their value and paste them as part of an example?

Consider an example where a Python example depends on the current directory.

Because you could be running byexample from anywhere, such example would likely fail: the output is not deterministic.

However you could paste the environment variable $PWD which has the current directory as the expected output.

$ cat test/ds/capture-env.doc               # byexample: +rm=  -tags
    >>> import os
    >>> assert '<PWD>' == os.getcwd()    # byexample: +paste

You just need to pass which variables from the environment will be in the clipboard of byexample so they can be pasted.

$ byexample -l python --capture-env-var PWD test/ds/capture-env.doc
[PASS] Pass: 2 Fail: 0 Skip: 0

You can capture as many environment variables as you want:

$ byexample -l python --capture-env-vars PWD,HOME,USER test/ds/capture-env.doc
[PASS] Pass: 2 Fail: 0 Skip: 0

Conditional execution on a captured environment variable

Perhaps the most useful combination is with conditionals.

Consider the following toy-example that it is executed unless the given environment variable is passed:

$ cat test/ds/capture-bomb.doc               # byexample: +rm= 
    $ echo "Booom!"    # byexample: +unless=bomb_disabled
    The bomb should not explode!

Running the example with an empty or unset variable bomb_disabled will make the example to run and fail (as expected, the bomb exploded).

$ echo $bomb_disabled  # empty, it is not set
$ byexample -l shell --capture-env-var bomb_disabled test/ds/capture-bomb.doc
The bomb should not explode!
[FAIL] Pass: 0 Fail: 1 Skip: 0

But setting anything to the variable we can skip the execution of the example.

$ export bomb_disabled=some
$ byexample -l shell --capture-env-var bomb_disabled test/ds/capture-bomb.doc
[PASS] Pass: 0 Fail: 0 Skip: 1

Note: in both cases bomb_disabled was put in the clipboard, this is required because +unless will complain if the variable is not there (empty or not empty).

New in byexample 10.1.0. This feature is marked as experimental.