cucumber/messages

JSON schema-based messages for Cucumber's inter-process communication

v25.0.1 2024-05-23 15:50 UTC

This package is auto-updated.

Last update: 2024-06-13 15:51:43 UTC


README

This is a PHP implementation of the Cucumber Messages protocol

Requirements

  • PHP 8.1
  • Ext-JSON

Installation

Install using composer.

composer require cucumber/messages

Usage

Consuming messages

Cucumber Messages are contained in a top-level Envelope object when serialised. Members are exposed via public readonly properties. Because many properties are nullable, it may be convenient to use the nullsafe operator to access them:

/** @var string|null $line */
$line = $envelope->gherkinDocument?->feature?->keyword;

Decoding JSON strings

You can construct an Envelope from a JSON string:

use Cucumber\Messages\DecodingException;
use Cucumber\Messages\Envelope;

try {
    $envelope = Envelope::fromJson($json);
}
catch (DecodingException $e) {
    // handle the error
}

Handling NDJSON Streams

Cucumber Messages are streamed as Newline Delimited JSON (NDJSON).

You can use the NdJsonStreamReader to obtain a Generator that produces Envelopes. It's important to remember that any decoding errors will be thrown as the generator is consumed, not when it's returned.

use Cucumber\Messages\DecodingException;
use Cucumber\Messages\Streams\NdJson\NdJsonStreamReader;
use Cucumber\Messages\Envelope;

$fh = fopen('messages.ndjson', 'r');
$reader = new NdJsonStreamReader($fh);

/** @var Generator<Envelope> $envelopes */
$envelopes = $reader->envelopes();

try {
    foreach ($envelopes as $envelope) {
        /** @var Envelope $envelope */
        // process the message
    }
}
catch (DecodingException $e) {
    // handle any errors here
}

Producing messages

All arguments of a Cucumber Message are optional, but any non-nullable fields will have default values.

Because Messages tend to have a large number of arguments, it's recommended to use named fields to construct them:

use Cucumber\Messages\Envelope;
use Cucumber\Messages\TestCaseFinished;
use Cucumber\Messages\Timestamp;

$envelope = new Envelope(
    testCaseFinished: new TestCaseFinished(
        timestamp: new Timestamp(
            seconds: 100
        )
    )
);

Encoding a JSON string

An Envelope can be encoded as a JSON string:

$json = $envelope->asJson();

Do not json_encode() the object externally, as the correct encoding options may not be set.

Producing JSON streams

Cucumber Messages are streamed as Newline Delimited JSON (NDJSON).

You can use the NdJsonStreamReader to write the contents of list of Envelopes to a stream.

use Cucumber\Messages\Streams\NdJson\NdJsonStreamReader;

$fh = fopen('php://stdout', 'w');

$writer = new NdJsonStreamWriter($fh)

// write a fixed array of envelopes
$envArray = [
    new Envelope('gherkinDocument': new GherkinDocument()),
    new Envelope('gherkinDocument': new GherkinDocument()),
];
$writer->write($envArray);

// write lazily-evaluated envelopes
$envGenerator = (function() {
    while ($envelope = Database::fetchNextEnvelope()) {
        yield $envelope;
    }
})();
$writer->write($envGenerator);