Stream Buffer Intercept

A PHP testing utility designed to capture stream output and facilitate writing unit tests for systems that require writing to streams.

Installation

composer require --dev cspray/stream-buffer-intercept

Usage Guide

There are scenarios where you may want to unit test some piece of code that writes to a stream. An example might be where you're writing tests to confirm log messages sent to stdout or stderr. The Cspray\StreamBufferIntercept\StreamBuffer class allows you to easily capture output sent to these streams, and others, to easily assert your expectations.

Let's take a look at a quick code example.

<?php declare(strict_types=1);

namespace Cspray\StreamBufferDemo;

use Cspray\StreamBufferIntercept\Buffer;
use Cspray\StreamBufferIntercept\StreamFilter;
use PHPUnit\Framework\TestCase;

class MyLogger {

    private $stdout;
    private $stderr;

    public function __construct($stdout, $stderr) {
        $this->stdout = $stdout;
        $this->stderr = $stderr;
    }
    
    public function log(string $message) : void {
        fwrite($this->stdout, $message);
    }
    
    public function logError(string $message) : void {
        fwrite($this->stderr, $message);
    }

}

class MyLoggerTest extends TestCase {

    private Buffer $stdout;
    
    private Buffer $stderr;
    
    private MyLogger $subject;
    
    protected function setUp() : void{
        StreamFilter::register();
        $this->stdout = StreamFilter::intercept(STDOUT);
        $this->stderr = StreamFilter::intercept(STDERR);
        $this->subject = new MyLogger(STDOUT, STDERR);
    }
    
    protected function tearDown() : void{
        $this->stdout->stopIntercepting();
        $this->stderr->stopIntercepting();
    }
    
    public function testLogMessageSentToStdOutAndNotStdErr() : void {
        $this->subject->log('My stdout output'); 
        
        self::assertSame('My stdout output', $this->stdout->output());
        self::assertSame('', $this->stderr->output());
    }

    public function testLogErrorMessageSentToStdErrAndNotStdOut() : void {
        $this->subject->logError('My stderr output'); 
        
        self::assertSame('My stderr output', $this->stderr->output());
        self::assertSame('', $this->stdout->output());
    }
}