Throw if extension is not installed when using NumberFormatter wrapper

As discussed in #internals, this seems to be a good compromise when the extension is not used. Instead of testing against the exception in the tests, I just skipped the test if the extension is missing, as that is what we do in the InteractsWithRedis testing trait.

src/Illuminate/Support/Number.php

@@ -2,6 +2,7 @@
 
 namespace Illuminate\Support;
 
+use RuntimeException;
 use Illuminate\Support\Traits\Macroable;
 use NumberFormatter;
 
@@ -18,6 +19,8 @@ class Number
      */
     public static function toHuman($number, $locale = 'en')
     {
+        static::needsIntlExtension();
+
         $formatter = new NumberFormatter($locale, NumberFormatter::SPELLOUT);
 
         return $formatter->format($number);
@@ -40,4 +43,18 @@ public static function bytesToHuman($bytes, $precision = 2)
 
         return sprintf('%s %s', round($bytes, $precision), $units[$i]);
     }
+
+    /**
+     * Some of the helper methods are wrappers for the PHP intl extension,
+     * and thus require it to be installed on the server. If it's not
+     * installed, we instead throw an exception from this method.
+     *
+     * @return void
+     */
+    protected static function needsIntlExtension()
+    {
+        if (! extension_loaded('intl')) {
+            throw new RuntimeException('The intl PHP extension is required to use this helper.');
+        }
+    }
 }

tests/Support/SupportNumberTest.php

@@ -9,6 +9,8 @@ class SupportNumberTest extends TestCase
 {
     public function testToHuman()
     {
+        $this->needsIntlExtension();
+
         $this->assertSame('zero', Number::toHuman(0));
         $this->assertSame('one', Number::toHuman(1));
         $this->assertSame('ten', Number::toHuman(10));
@@ -34,6 +36,8 @@ public function testToHuman()
 
     public function testToHumanWithDifferentLocale()
     {
+        $this->needsIntlExtension();
+
         $this->assertSame('cent vingt-trois', Number::toHuman(123, 'fr'));
 
         $this->assertSame('ein­hundert­drei­und­zwanzig', Number::toHuman(123, 'de'));
@@ -56,4 +60,11 @@ public function testBytesToHuman()
         $this->assertSame('1 YB', Number::bytesToHuman(1024 ** 8));
         $this->assertSame('1024 YB', Number::bytesToHuman(1024 ** 9));
     }
+
+    protected function needsIntlExtension()
+    {
+        if (!extension_loaded('intl')) {
+            $this->markTestSkipped('The intl extension is not installed. Please install the extension to enable ' . __CLASS__);
+        }
+    }
 }