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

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Setup and Tear Down

Sometimes you need to handle resources in the tests: you need to make sure that you have them before running any test and you need to release them at the end.

Think in a web server, a virtual machine, a database connection.

Let’s take the last one.

Imagine that you want to show how to interact with your database to explain the underlying model and relationships. You obviously need to setup the database first with some dataset in order to show how to interact with it.

It is also reasonable to tear down the database connection at the end.

You could write:

$ cat test/ds/db-stock-model                         # byexample: +rm= 
This is a quick introduction to the database schema.
     >>> import sqlite3
     >>> c = sqlite3.connect(':memory:')
     >>> _ = c.executescript(open('test/ds/stock.sql').read())  # ---> # byexample: +fail-fast
Get the stocks' prices
     >>> _ = c.execute('select price from stocks')
Do not forget to close the connection
     >>> c.close()                         # ---> # byexample: -skip

In a happy and perfect world this should run smoothly:

$ byexample -l python test/ds/db-stock-model
File test/ds/db-stock-model, 5/5 test ran in <...> seconds
[PASS] Pass: 5 Fail: 0 Skip: 0

Now, if for some reason you cannot load the initial dump, it makes sense to stop the whole execution: this is known as fail fast and it is archived with the +fail-fast flag.

This should skip all the examples, however no matter what happen, you always want to leave a clean environment and close the connection: you can force this saying that the example must not be skipped (-skip).

Check what happen if we delete the sql file: the example c.executescript should fail and because +fail-safe is in effect for, the rest of the example should be skippped except the last one because explicitly says do not skip me with -skip.

$ mv test/ds/stock.sql test/ds/renamed.sql

$ byexample -l python test/ds/db-stock-model
File test/ds/db-stock-model, 5/5 test ran in <...> seconds
[FAIL] Pass: 3 Fail: 1 Skip: 1

Note: in some cases byexample may not be able to recover the control of the runner after a timeout.

In those cases or when the runner crash directly, the execution will abort immediately without executing any example even if they have -skip. This is because these kind of failures may had left the interpreter in a invalid state and the execution cannot be resumed.

The best strategy would be create a concern module and hook to the finish event and perform there all the clean up, if any.

Changed in byexample 8.0.0: before, a timeout had always ended in an abort without doing any clean up. But in 8.0.0 this changed and an abort is much more rare. See timeout doc.