TestSlide’s DSL¶

When testing complex scenarios with lots of variations, or when doing BDD, TestSlide’s DSL helps you break down your test cases close to spoken language. Composition of test scenarios enables covering more ground with less effort. Think of it as unittest.TestCase on steroids.

Let’s say we want to test this class:

import storage

class Backup:
  def __init__(self):
    self.storage = storage.Client(timeout=60)

  def delete(self, path):
    self.storage.delete(path)

We can test use it with:

from testslide.dsl import context
from testslide import StrictMock
import storage
import backup

@context
def Backup(context):

  context.memoize("backup", lambda self: backup.Backup())

  context.memoize("storage_mock", lambda self: StrictMock(storage.Client))

  @context.before
  def mock_storage_Client(self):
    self.mock_constructor(storage, 'Client')\
      .for_call(timeout=60)\
      .to_return_value(self.storage_mock)

  @context.sub_context
  def delete(context):
    context.memoize("path", lambda self: '/some/file')

    @context.after
    def call_backup_delete(self):
      self.backup.delete(self.path)

    @context.example
    def it_deletes_from_storage_backend(self):
      self.mock_callable(self.storage_mock, 'delete')\
        .for_call(self.path)\
        .to_return_value(True)\
        .and_assert_called_once()

And when we run it:

$ testslide backup_test.py
Backup
  delete
    it deletes from storage backend

Finished 1 example(s) in 0.0s:
  Successful: 1

As you can see, we can declare contexts for testing, and keep building on top of them:

The top Backup context contains the object we want to test, and the common mocks needed.
The nested delete context always calls Backup.delete after each example.
The it_deletes_from_storage_backend example defines only the assertion needed for it.

As the Backup class grows, it is easy to nest new contexts, and reuse what’s already defined.