This Pipeline was created to reduce testing boilerplate and ease communication with its children. It also provides a utility for informing testing process about playback state changes and received notifications.

When you want a build Pipeline to test your children you need three things:

• Pipeline Module
• List of children
• Links between those children

To start a testing pipeline you need to build a keyword list representing the options used to determine the pipeline's behaviour and then pass that options list to the Membrane.Testing.Pipeline.start_link/2. The testing pipeline can be started in one of two modes - either with its :default behaviour, or by injecting a custom module behaviour. The usage of a :default pipeline implementation is presented below:

children = [
    el1: MembraneElement1,
    el2: MembraneElement2,
    ...
]
options =  [
  module: :default # :default is the default value for this parameter, so you do not need to pass it here
  links: Membrane.ParentSpec.link_linear(children)
]
{:ok, pipeline} = Membrane.Testing.Pipeline.start_link(options)

Note, that we have used Membrane.Testing.ParentSpec.link_linear/1 function, that creates the list of links for the given list of children, linking them in linear manner (that means - children are linked in a way that :output pad of a given child is linked to :input pad of subsequent child). That is the case which is often used while creating testing pipelines. Be aware, that Membrane.Testing.ParentSpec.link_linear/1 creates also a children specification itself, which means, that you cannot pass that children specification as another option's argument (adding children: children option would lead to a duplication of children specifications). If you need to link children in a different manner, you can of course do it by passing an appropriate list of links as a :links option, just as you would do with a regular pipeline.

You can also pass your custom pipeline's module as a :module option of the options list. Every callback of the module will be executed before the callbacks of Testing.Pipeline. Passed module has to return a proper spec. There should be no children nor links specified in options passed to test pipeline as that would result in a failure.

options = [
  module: Your.Module
]
{:ok, pipeline} = Membrane.Testing.Pipeline.start_link(options)

See Membrane.Testing.Pipeline.pipeline_keyword_list_t() for available options.

assertions

Assertions

This pipeline is designed to work with Membrane.Testing.Assertions. Check them out or see example below for more details.

messaging-children

Messaging children

You can send messages to children using their names specified in the children list. Please check message_child/3 for more details.

example-usage

Example usage

Firstly, we can start the pipeline providing its options as a keyword list:

children = [
    source: %Membrane.Testing.Source{},
    tested_element: TestedElement,
    sink: %Membrane.Testing.Sink{}
]
{:ok, pipeline} = Membrane.Testing.Pipeline.start_link(links: Membrane.ParentSpec.link_linear(children))

We can now wait till the end of the stream reaches the sink element (don't forget to import Membrane.Testing.Assertions):

assert_end_of_stream(pipeline, :sink)

We can also assert that the Membrane.Testing.Sink processed a specific buffer:

assert_sink_buffer(pipeline, :sink, %Membrane.Buffer{payload: 1})