minor #18519 [Process] Consistently use getProcess() in tests (nicolas-grekas)

This PR was merged into the 2.7 branch.

Discussion
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[Process] Consistently use getProcess() in tests

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
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ce13fe7 [Process] Consistently use getProcess() in tests

Author: nicolas-grekas

src/Symfony/Component/Process/Tests/ProcessTest.php

@@ -1181,7 +1181,7 @@ public function pipesCodeProvider()
      * @dataProvider provideVariousIncrementals
      */
     public function testIncrementalOutputDoesNotRequireAnotherCall($stream, $method) {
-        $process = new Process(self::$phpBin.' -r '.escapeshellarg('$n = 0; while ($n < 3) { file_put_contents(\''.$stream.'\', $n, 1); $n++; usleep(1000); }'), null, null, null, null);
+        $process = $this->getProcess(self::$phpBin.' -r '.escapeshellarg('$n = 0; while ($n < 3) { file_put_contents(\''.$stream.'\', $n, 1); $n++; usleep(1000); }'), null, null, null, null);
         $process->start();
         $result = '';
         $limit = microtime(true) + 3;