minor #11565 [Process] Added process synchronization to the increment…

…al output tests (webmozart)

This PR was merged into the 2.3 branch.

Discussion
----------

[Process] Added process synchronization to the incremental output tests

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

The tests currently fail from time to time if the executing machine is under
heavy load. This leads to false negatives on Travis CI.

A side effect of the change is that the tests are much faster now.

Commits
-------

6dd3946 [Process] Added process synchronization to the incremental output tests

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

@@ -259,32 +259,52 @@ public function testGetErrorOutput()
 
     public function testGetIncrementalErrorOutput()
     {
-        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n = 0; while ($n < 3) { usleep(100000); file_put_contents(\'php://stderr\', \'ERROR\'); $n++; }')));
+        // use a lock file to toggle between writing ("W") and reading ("R") the
+        // error stream
+        $lock = tempnam(sys_get_temp_dir(), get_class($this).'Lock');
+        file_put_contents($lock, 'W');
+
+        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n = 0; while ($n < 3) { if (\'W\' === file_get_contents('.var_export($lock, true).')) { file_put_contents(\'php://stderr\', \'ERROR\'); $n++; file_put_contents('.var_export($lock, true).', \'R\'); } usleep(100); }')));
 
         $p->start();
         while ($p->isRunning()) {
-            $this->assertLessThanOrEqual(1, preg_match_all('/ERROR/', $p->getIncrementalErrorOutput(), $matches));
-            usleep(20000);
+            if ('R' === file_get_contents($lock)) {
+                $this->assertLessThanOrEqual(1, preg_match_all('/ERROR/', $p->getIncrementalErrorOutput(), $matches));
+                file_put_contents($lock, 'W');
+            }
+            usleep(100);
         }
+
+        unlink($lock);
     }
 
     public function testGetOutput()
     {
-        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n=0;while ($n<3) {echo \' foo \';$n++; usleep(500); }')));
+        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n = 0; while ($n < 3) { echo \' foo \'; $n++; }')));
 
         $p->run();
         $this->assertEquals(3, preg_match_all('/foo/', $p->getOutput(), $matches));
     }
 
     public function testGetIncrementalOutput()
     {
-        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n=0;while ($n<3) { echo \' foo \'; usleep(50000); $n++; }')));
+        // use a lock file to toggle between writing ("W") and reading ("R") the
+        // output stream
+        $lock = tempnam(sys_get_temp_dir(), get_class($this).'Lock');
+        file_put_contents($lock, 'W');
+
+        $p = $this->getProcess(sprintf('php -r %s', escapeshellarg('$n = 0; while ($n < 3) { if (\'W\' === file_get_contents('.var_export($lock, true).')) { echo \' foo \'; $n++; file_put_contents('.var_export($lock, true).', \'R\'); } usleep(100); }')));
 
         $p->start();
         while ($p->isRunning()) {
-            $this->assertLessThanOrEqual(1, preg_match_all('/foo/', $p->getIncrementalOutput(), $matches));
-            usleep(20000);
+            if ('R' === file_get_contents($lock)) {
+                $this->assertLessThanOrEqual(1, preg_match_all('/foo/', $p->getIncrementalOutput(), $matches));
+                file_put_contents($lock, 'W');
+            }
+            usleep(100);
         }
+
+        unlink($lock);
     }
 
     public function testZeroAsOutput()