diff --git a/composer.json b/composer.json
index 4cb6b38..cce41ef 100644
--- a/composer.json
+++ b/composer.json
@@ -15,9 +15,7 @@
         "psr-4": {
             "Toalett\\Multiprocessing\\": ["src"]
         },
-        "exclude-from-classmap": [
-            "**/Tests/"
-        ]
+        "exclude-from-classmap": ["src/Tests/"]
     },
     "autoload-dev": {
         "psr-4": {
@@ -33,6 +31,6 @@
     "extra": {
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5.0"
+        "phpunit/phpunit": "^9.5"
     }
 }
diff --git a/composer.lock b/composer.lock
index 9bd941f..9386521 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "e6e2d2021fce4df2143d382fe26302e7",
+    "content-hash": "431bed10aaf05c9691db445c588f6262",
     "packages": [
         {
             "name": "evenement/evenement",
diff --git a/src/Context.php b/src/Context.php
index d0e29c1..b947e96 100644
--- a/src/Context.php
+++ b/src/Context.php
@@ -29,7 +29,7 @@ class Context implements EventEmitterInterface
 
 		$this->workers->on('worker_started', fn(int $pid) => $this->emit('worker_started', [$pid]));
 		$this->workers->on('worker_stopped', fn(int $pid) => $this->emit('worker_stopped', [$pid]));
-		$this->workers->on('worker_stopped', fn() => $this->emitIf($this->workers->empty(), 'no_workers_remaining'));
+		$this->workers->on('worker_stopped', fn() => $this->emitIf(empty($this->workers), 'no_workers_remaining'));
 	}
 
 	public function submit(callable $task, ...$args): void
diff --git a/src/ProcessControl/Fork.php b/src/ProcessControl/Fork.php
new file mode 100644
index 0000000..b953766
--- /dev/null
+++ b/src/ProcessControl/Fork.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Toalett\Multiprocessing\ProcessControl;
+
+class Fork
+{
+	public int $pid;
+
+	public function __construct(int $pid)
+	{
+		$this->pid = $pid;
+	}
+
+	public function failed(): bool
+	{
+		return $this->pid < 0;
+	}
+
+	public function isChild(): bool
+	{
+		return $this->pid === 0;
+	}
+
+	public function isParent(): bool
+	{
+		return $this->pid !== 0;
+	}
+}
diff --git a/src/ProcessControl/PCNTL.php b/src/ProcessControl/PCNTL.php
new file mode 100644
index 0000000..8728c52
--- /dev/null
+++ b/src/ProcessControl/PCNTL.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Toalett\Multiprocessing\ProcessControl;
+
+class PCNTL implements ProcessControl
+{
+	public function fork(): Fork
+	{
+		$pid = pcntl_fork();
+		return new Fork($pid);
+	}
+
+	public function wait(int $options = 0): Wait
+	{
+		$pid = pcntl_wait($status, $options);
+		return new Wait($pid, $status);
+	}
+}
diff --git a/src/ProcessControl/ProcessControl.php b/src/ProcessControl/ProcessControl.php
new file mode 100644
index 0000000..184b06f
--- /dev/null
+++ b/src/ProcessControl/ProcessControl.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Toalett\Multiprocessing\ProcessControl;
+
+interface ProcessControl
+{
+	public function fork(): Fork;
+
+	public function wait(int $options = 0): Wait;
+}
diff --git a/src/ProcessControl/Wait.php b/src/ProcessControl/Wait.php
new file mode 100644
index 0000000..a35369f
--- /dev/null
+++ b/src/ProcessControl/Wait.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Toalett\Multiprocessing\ProcessControl;
+
+class Wait
+{
+	public int $pid;
+	public int $status;
+
+	public function __construct(int $pid, int $status = 0)
+	{
+		$this->pid = $pid;
+		$this->status = $status;
+	}
+
+	public function childStopped(): bool
+	{
+		return $this->pid > 0;
+	}
+
+	public function failed(): bool
+	{
+		return $this->pid < 0;
+	}
+}
diff --git a/src/Tests/ProcessControl/ForkTest.php b/src/Tests/ProcessControl/ForkTest.php
new file mode 100644
index 0000000..88297c7
--- /dev/null
+++ b/src/Tests/ProcessControl/ForkTest.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Toalett\Multiprocessing\Tests\ProcessControl;
+
+use PHPUnit\Framework\TestCase;
+use Toalett\Multiprocessing\ProcessControl\Fork;
+
+class ForkTest extends TestCase
+{
+	/**
+	 * @param int $pid
+	 * @dataProvider positiveIntegerProvider
+	 */
+	public function testItSaysItIsAParentProcessWhenAPositivePidIsProvided(int $pid): void
+	{
+		$fork = new Fork($pid);
+		self::assertTrue($fork->isParent());
+		self::assertFalse($fork->isChild());
+		self::assertFalse($fork->failed());
+	}
+
+	/**
+	 * @param int $pid
+	 * @dataProvider negativeIntegerProvider
+	 */
+	public function testItSaysItFailedWhenANegativePidIsProvided(int $pid): void
+	{
+		$fork = new Fork($pid);
+		self::assertTrue($fork->isParent());
+		self::assertFalse($fork->isChild());
+		self::assertTrue($fork->failed());
+	}
+
+	public function testItSaysItIsAChildProcessWhenPidZeroIsProvided(): void
+	{
+		$fork = new Fork(0);
+		self::assertFalse($fork->isParent());
+		self::assertTrue($fork->isChild());
+		self::assertFalse($fork->failed());
+	}
+
+	public function positiveIntegerProvider(): array
+	{
+		return [
+			[1],
+			[10],
+			[1000],
+			[PHP_INT_MAX],
+		];
+	}
+
+	public function negativeIntegerProvider(): array
+	{
+		return [
+			[-1],
+			[-10],
+			[-1000],
+			[PHP_INT_MIN],
+		];
+	}
+}
diff --git a/src/Tests/ProcessControl/WaitTest.php b/src/Tests/ProcessControl/WaitTest.php
new file mode 100644
index 0000000..62585f5
--- /dev/null
+++ b/src/Tests/ProcessControl/WaitTest.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Toalett\Multiprocessing\Tests\ProcessControl;
+
+use PHPUnit\Framework\TestCase;
+use Toalett\Multiprocessing\ProcessControl\Wait;
+
+class WaitTest extends TestCase
+{
+	/**
+	 * @param int $pid
+	 * @dataProvider positiveIntegerProvider
+	 */
+	public function testItSaysAChildStoppedWhenAPositivePidIsProvided(int $pid): void
+	{
+		$wait = new Wait($pid, 0);
+		self::assertTrue($wait->childStopped());
+		self::assertFalse($wait->failed());
+	}
+
+	/**
+	 * @param int $pid
+	 * @dataProvider negativeIntegerProvider
+	 */
+	public function testItSaysItFailedWhenANegativePidIsProvided(int $pid): void
+	{
+		$wait = new Wait($pid, 0);
+		self::assertFalse($wait->childStopped());
+		self::assertTrue($wait->failed());
+	}
+
+	public function positiveIntegerProvider(): array
+	{
+		return [
+			[1],
+			[10],
+			[1000],
+			[PHP_INT_MAX],
+		];
+	}
+
+	public function negativeIntegerProvider(): array
+	{
+		return [
+			[-1],
+			[-10],
+			[-1000],
+			[PHP_INT_MIN],
+		];
+	}
+}
diff --git a/src/Tests/WorkersTest.php b/src/Tests/WorkersTest.php
index 61d7c7f..91da5a9 100644
--- a/src/Tests/WorkersTest.php
+++ b/src/Tests/WorkersTest.php
@@ -2,22 +2,55 @@
 
 namespace Toalett\Multiprocessing\Tests;
 
-use ReflectionObject;
-use Toalett\Multiprocessing\Workers;
 use PHPUnit\Framework\TestCase;
+use ReflectionObject;
+use Toalett\Multiprocessing\ProcessControl\Fork;
+use Toalett\Multiprocessing\ProcessControl\ProcessControl;
+use Toalett\Multiprocessing\ProcessControl\Wait;
+use Toalett\Multiprocessing\Workers;
 
 class WorkersTest extends TestCase
 {
+	public function testItSaysItIsEmptyWhenNoWorkers(): void
+	{
+		$processControl = $this->createMock(ProcessControl::class);
+		$workers = new Workers($processControl);
+		self::assertEmpty($workers);
+	}
+
+	public function testItSaysItHasOneWorkerWhenTaskExecutes(): void
+	{
+		$workers = new Workers();
+
+		$workers->createWorkerFor(fn() => exit(0), []);
+		self::assertCount(1, $workers);
+	}
+
+	public function testItGivesTheAmountOfActiveWorkersOnCount(): void
+	{
+		$workers = new Workers();
+
+		$workers->createWorkerFor(fn() => exit(0), []);
+		$workers->createWorkerFor(fn() => exit(0), []);
+		self::assertCount(2, $workers);
+
+		$workers->createWorkerFor(fn() => exit(0), []);
+		self::assertCount(3, $workers);
+
+		$workers->stop();
+		self::assertEmpty($workers);
+	}
+
 	public function testItEmitsAnEventWhenAWorkerIsStarted(): void
 	{
 		$workers = new Workers();
 
 		$workerStartedEventHasTakenPlace = false;
-		$workers->on('worker_started', function() use (&$workerStartedEventHasTakenPlace) {
+		$workers->on('worker_started', function () use (&$workerStartedEventHasTakenPlace) {
 			$workerStartedEventHasTakenPlace = true;
 		});
-
 		self::assertFalse($workerStartedEventHasTakenPlace);
+
 		$workers->createWorkerFor(fn() => exit(0), []);
 		self::assertTrue($workerStartedEventHasTakenPlace);
 	}
@@ -30,7 +63,7 @@ class WorkersTest extends TestCase
 		$method->setAccessible(true);
 
 		$workerStoppedEventHasTakenPlace = false;
-		$workers->on('worker_stopped', function() use (&$workerStoppedEventHasTakenPlace) {
+		$workers->on('worker_stopped', function () use (&$workerStoppedEventHasTakenPlace) {
 			$workerStoppedEventHasTakenPlace = true;
 		});
 
@@ -38,4 +71,39 @@ class WorkersTest extends TestCase
 		$method->invoke($workers, 0);
 		self::assertTrue($workerStoppedEventHasTakenPlace);
 	}
+
+	public function testItCallsForkOnProcessControlWhenAskedToCreateAWorker(): void
+	{
+		$processControl = $this->createMock(ProcessControl::class);
+		$processControl->expects(self::once())
+			->method('fork')
+			->willReturn(new Fork(1));
+
+		$workers = new Workers($processControl);
+		$workers->createWorkerFor(fn() => []);
+	}
+
+	public function testItCallsNonBlockingWaitOnProcessControlWhenPerformingCleanup(): void
+	{
+		$processControl = $this->createMock(ProcessControl::class);
+		$processControl->expects(self::once())
+			->method('wait')
+			->with(WNOHANG)
+			->willReturn(new Wait(0));
+
+		$workers = new Workers($processControl);
+		$workers->cleanup();
+	}
+
+	public function testItCallsBlockingWaitOnProcessControlWhenAwaitingCongestionRelief(): void
+	{
+		$processControl = $this->createMock(ProcessControl::class);
+		$processControl->expects(self::once())
+			->method('wait')
+			->with(/* no arguments */)
+			->willReturn(new Wait(1));
+
+		$workers = new Workers($processControl);
+		$workers->awaitCongestionRelief();
+	}
 }
diff --git a/src/Workers.php b/src/Workers.php
index a7af96f..f88d9ff 100644
--- a/src/Workers.php
+++ b/src/Workers.php
@@ -7,6 +7,8 @@ use Evenement\EventEmitterInterface;
 use Evenement\EventEmitterTrait;
 use Throwable;
 use Toalett\Multiprocessing\Exception\ProcessControlException;
+use Toalett\Multiprocessing\ProcessControl\PCNTL;
+use Toalett\Multiprocessing\ProcessControl\ProcessControl;
 
 class Workers implements Countable, EventEmitterInterface
 {
@@ -14,18 +16,19 @@ class Workers implements Countable, EventEmitterInterface
 
 	/** @var int[] */
 	private array $workers = [];
+	private ProcessControl $processControl;
+
+	public function __construct(?ProcessControl $processControl = null)
+	{
+		$this->processControl = $processControl ?? new PCNTL();
+	}
 
 	public function count(): int
 	{
 		return count($this->workers);
 	}
 
-	public function empty(): bool
-	{
-		return count($this->workers) === 0;
-	}
-
-	public function createWorkerFor(callable $task, array $args): void
+	public function createWorkerFor(callable $task, array $args = []): void
 	{
 		$pid = $this->forkWorker($task, $args);
 		$this->workers[$pid] = $pid;
@@ -50,12 +53,12 @@ class Workers implements Countable, EventEmitterInterface
 
 	private function forkWorker(callable $task, array $args): int
 	{
-		$pid = pcntl_fork();
-		if ($pid === -1) {
+		$fork = $this->processControl->fork();
+		if ($fork->failed()) {
 			throw ProcessControlException::forkFailed();
 		}
 
-		if ($pid === 0) {
+		if ($fork->isChild()) {
 			try {
 				call_user_func_array($task, $args);
 			} catch (Throwable $t) {
@@ -65,7 +68,7 @@ class Workers implements Countable, EventEmitterInterface
 			exit(0);
 		}
 
-		return $pid;
+		return $fork->pid;
 	}
 
 	/**
@@ -74,9 +77,9 @@ class Workers implements Countable, EventEmitterInterface
 	 */
 	private function wait(int $options = 0): bool
 	{
-		$pid = pcntl_wait($status, $options);
-		if ($pid > 0) {
-			$this->remove($pid);
+		$wait = $this->processControl->wait($options);
+		if ($wait->childStopped()) {
+			$this->remove($wait->pid);
 			return true;
 		}
 		// We ignore errors ($pid < 0). This method is called periodically, even if there is
@@ -86,6 +89,6 @@ class Workers implements Countable, EventEmitterInterface
 
 	public function stop(): void
 	{
-		while (true === $this->wait());
+		while (true === $this->wait()) ;
 	}
 }