Allow to define parallel-limit option to run command (fixes #210)

CHANGELOG.md

@@ -5,6 +5,7 @@
 ## Unreleased
 ### Added
 - Detect readiness state of new Selenium servers (v3.5.3+ running in W3C-protocol mode) during startup, so that eg. no available Selenium server nodes are reported before attempting to start any test.
+- `--parallel-limit` (`-l`) option of `run` command to allow limiting maximum number of tests being run simultaneously.
 
 ### Changed
 - Require PHP 7.1+ and Symfony 4 components.

README.md

@@ -161,6 +161,7 @@ There is also a bunch of useful options for the `run` command:
 - `--server-url` - set different url of selenium server than the default (which is `http://localhost:4444/wd/hub`)
 - `--xdebug` - start Xdebug debugger on your tests. Allows you to debug tests from your IDE ([learn more about tests debugging][wiki-debugging] in our Wiki)
 - `--capability` - directly pass any extra capability to the Selenium WebDriver server ([see wiki][wiki-capabilities] for more information and examples)
+- `--parallel-limit` - limit number of testcases being executed in a parallel (default is 50)
 - `--help` - see all other options and default values
 - **adjust output levels:** by default, only the test results summary is printed to the output; the verbosity could be changed by the following:
     - `-v` - to instantly output name of failed test(s)

src-tests/Console/Command/Fixtures/FailingTests/expected-very-verbose-output.txt

@@ -3,6 +3,7 @@ Browser: chrome
 Environment: staging
 Path to logs: %s/logs
 Ignore delays: no
+Parallel limit: 50
 Selenium server (hub) url: %s, trying connection...OK
 Searching for testcases:
  - in directory %s/src-tests/Console/Command/Fixtures/FailingTests"

src-tests/Console/Command/Fixtures/SimpleTests/expected-debug-output.txt

@@ -3,6 +3,7 @@ Browser: chrome
 Environment: staging
 Path to logs: %s/logs
 Ignore delays: no
+Parallel limit: 50
 Selenium server (hub) url: %s, trying connection...OK
 Searching for testcases:
  - in directory "%s/src-tests/Console/Command/Fixtures/SimpleTests"

src-tests/Console/Command/Fixtures/SimpleTests/expected-very-verbose-output.txt

@@ -3,6 +3,7 @@ Browser: chrome
 Environment: staging
 Path to logs: %s/logs
 Ignore delays: no
+Parallel limit: 50
 Selenium server (hub) url: %s, trying connection...OK
 Searching for testcases:
  - in directory "%s/src-tests/Console/Command/Fixtures/SimpleTests"

src/Console/Command/RunCommand.php

@@ -51,6 +51,7 @@ class RunCommand extends Command
     public const OPTION_FILTER = 'filter';
     public const OPTION_NO_EXIT = 'no-exit';
     public const OPTION_IGNORE_DELAYS = 'ignore-delays';
+    public const OPTION_PARALLEL_LIMIT = 'parallel-limit';
 
     /**
      * @internal
@@ -148,6 +149,13 @@ protected function configure(): void
                 'i',
                 InputOption::VALUE_NONE,
                 'Ignore delays defined between testcases'
+            )
+            ->addOption(
+                self::OPTION_PARALLEL_LIMIT,
+                'l',
+                InputOption::VALUE_REQUIRED,
+                'Number of maximum testcases being executed in a parallel',
+                50
             );
 
         $this->addUsage('staging firefox');
@@ -204,6 +212,13 @@ protected function initialize(InputInterface $input, OutputInterface $output): v
         $seleniumAdapter = $this->getSeleniumAdapter($input->getOption(self::OPTION_SERVER_URL));
         $input->setOption(self::OPTION_SERVER_URL, $seleniumAdapter->getServerUrl());
 
+        // Make sure parallel-limit is greater than 0
+        $parallelLimit = (int) $input->getOption(self::OPTION_PARALLEL_LIMIT);
+        if ($parallelLimit === 0) {
+            throw new \RuntimeException('Parallel limit must be a whole number greater than 0');
+        }
+        $input->setOption(self::OPTION_PARALLEL_LIMIT, $parallelLimit);
+
         $this->getDispatcher()->dispatch(
             CommandEvents::RUN_TESTS_INIT,
             new ExtendedConsoleEvent($this, $input, $output)
@@ -216,6 +231,9 @@ protected function initialize(InputInterface $input, OutputInterface $output): v
             $output->writeln(
                 sprintf('Ignore delays: %s', ($input->getOption(self::OPTION_IGNORE_DELAYS)) ? 'yes' : 'no')
             );
+            $output->writeln(
+                sprintf('Parallel limit: %d', $input->getOption(self::OPTION_PARALLEL_LIMIT))
+            );
         }
     }
 
@@ -263,7 +281,9 @@ protected function execute(InputInterface $input, OutputInterface $output): int
             return 1;
         }
 
-        $executionLoop = new ExecutionLoop($processSet, $this->io, new MaxTotalDelayStrategy());
+        $maxParallelLimit = $input->getOption(self::OPTION_PARALLEL_LIMIT);
+
+        $executionLoop = new ExecutionLoop($processSet, $this->io, new MaxTotalDelayStrategy(), $maxParallelLimit);
 
         $allTestsPassed = $executionLoop->start();