Throw exception upon failure instead of arbitrary default value (#21)

The reasoning is that depending of the context, one may want to apply a different arbitrary default value. It is easier to do that by wrapping the call in a try/catch catching a specific exception rather than getting the value directly (since you wouldn't know if you get the right value found, or the default one).

src/CpuCoreCounter.php

@@ -26,14 +26,16 @@ final class CpuCoreCounter
     private int $count;
 
     /**
-     * @param list<CpuCoreFinder> $finders
+     * @param list<CpuCoreFinder>|null $finders
      */
     public function __construct(?array $finders = null)
     {
         $this->finders = $finders ?? self::getDefaultFinders();
     }
 
     /**
+     * @throws NumberOfCpuCoreNotFound
+     *
      * @return positive-int
      */
     public function getCount(): int
@@ -47,6 +49,8 @@ public function getCount(): int
     }
 
     /**
+     * @throws NumberOfCpuCoreNotFound
+     *
      * @return positive-int
      */
     private function findCount(): int
@@ -63,7 +67,7 @@ private function findCount(): int
             }
         }
 
-        return 2;
+        throw NumberOfCpuCoreNotFound::create();
     }
 
     /**

src/NumberOfCpuCoreNotFound.php

@@ -0,0 +1,26 @@
+<?php
+
+/*
+ * This file is part of the Fidry CPUCounter Config package.
+ *
+ * (c) Théo FIDRY <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Fidry\CpuCounter;
+
+use RuntimeException;
+
+final class NumberOfCpuCoreNotFound extends RuntimeException
+{
+    public static function create(): self
+    {
+        return new self(
+            'Could not find the number of CPU cores available.',
+        );
+    }
+}

tests/CpuCoreCounterTest.php

@@ -13,8 +13,12 @@
 
 namespace Fidry\CpuCounter\Test;
 
+use Exception;
 use Fidry\CpuCounter\CpuCoreCounter;
+use Fidry\CpuCounter\NumberOfCpuCoreNotFound;
 use PHPUnit\Framework\TestCase;
+use function get_class;
+use function is_int;
 
 /**
  * @covers \Fidry\CpuCounter\CpuCoreCounter
@@ -34,23 +38,38 @@ public function test_it_can_get_the_number_of_cpu_cores(): void
      * @dataProvider cpuCoreFinderProvider
      *
      * @param list<CpuCoreCounter> $finders
+     * @param int|Exception        $expected
      */
     public function test_it_can_get_the_number_of_cpu_cores_based_on_the_registered_finders(
         array $finders,
-        int $expected
+        $expected
     ): void {
         $counter = new CpuCoreCounter($finders);
 
-        $actual = $counter->getCount();
+        if (is_int($expected)) {
+            $actual = $counter->getCount();
 
-        self::assertSame($expected, $actual);
+            self::assertSame($expected, $actual);
+
+            return;
+        }
+
+        // Sanity check
+        self::assertTrue($expected instanceof Exception);
+
+        $this->expectException(get_class($expected));
+        $this->expectExceptionMessage($expected->getMessage());
+
+        $counter->getCount();
     }
 
     public static function cpuCoreFinderProvider(): iterable
     {
+        $defaultException = NumberOfCpuCoreNotFound::create();
+
         yield 'no finder' => [
             [],
-            2,
+            $defaultException,
         ];
 
         yield 'single finder finds a value' => [
@@ -64,7 +83,7 @@ public static function cpuCoreFinderProvider(): iterable
             [
                 new DummyCpuCoreFinder(null),
             ],
-            2,
+            $defaultException,
         ];
 
         yield 'multiple finders find a value' => [