Source code for apache_beam.testing.util

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"""Utilities for testing Beam pipelines."""

from __future__ import absolute_import

from apache_beam import pvalue
from apache_beam.transforms import window
from apache_beam.transforms.core import Create
from apache_beam.transforms.core import Map
from apache_beam.transforms.core import WindowInto
from apache_beam.transforms.util import CoGroupByKey
from apache_beam.transforms.ptransform import PTransform


__all__ = [
    'assert_that',
    'equal_to',
    'is_empty',
    ]


class BeamAssertException(Exception):
  """Exception raised by matcher classes used by assert_that transform."""

  pass


# Note that equal_to always sorts the expected and actual since what we
# compare are PCollections for which there is no guaranteed order.
# However the sorting does not go beyond top level therefore [1,2] and [2,1]
# are considered equal and [[1,2]] and [[2,1]] are not.
# TODO(silviuc): Add contains_in_any_order-style matchers.
def equal_to(expected):
  expected = list(expected)

  def _equal(actual):
    sorted_expected = sorted(expected)
    sorted_actual = sorted(actual)
    if sorted_expected != sorted_actual:
      raise BeamAssertException(
          'Failed assert: %r == %r' % (sorted_expected, sorted_actual))
  return _equal


def is_empty():
  def _empty(actual):
    actual = list(actual)
    if actual:
      raise BeamAssertException(
          'Failed assert: [] == %r' % actual)
  return _empty


def assert_that(actual, matcher, label='assert_that'):
  """A PTransform that checks a PCollection has an expected value.

  Note that assert_that should be used only for testing pipelines since the
  check relies on materializing the entire PCollection being checked.

  Args:
    actual: A PCollection.
    matcher: A matcher function taking as argument the actual value of a
      materialized PCollection. The matcher validates this actual value against
      expectations and raises BeamAssertException if they are not met.
    label: Optional string label. This is needed in case several assert_that
      transforms are introduced in the same pipeline.

  Returns:
    Ignored.
  """
  assert isinstance(actual, pvalue.PCollection)

  class AssertThat(PTransform):

    def expand(self, pcoll):
      # We must have at least a single element to ensure the matcher
      # code gets run even if the input pcollection is empty.
      keyed_singleton = pcoll.pipeline | Create([(None, None)])
      keyed_actual = (
          pcoll
          | WindowInto(window.GlobalWindows())
          | "ToVoidKey" >> Map(lambda v: (None, v)))
      _ = ((keyed_singleton, keyed_actual)
           | "Group" >> CoGroupByKey()
           | "Unkey" >> Map(lambda (k, (_, actual_values)): actual_values)
           | "Match" >> Map(matcher))

    def default_label(self):
      return label

  actual | AssertThat()  # pylint: disable=expression-not-assigned