fix(isbn13): update ISBN-13 generation logic and examples

src/Faker/Core/Barcode.php

@@ -45,7 +45,17 @@ public function isbn10(): string
 
     public function isbn13(): string
     {
-        $code = '97' . $this->numberExtension->numberBetween(8, 9) . Extension\Helper::numerify(str_repeat('#', 9));
+        $prefix = '97' . $this->numberExtension->numberBetween(8, 9);
+        $group = $this->numberExtension->numberBetween($prefix === '978' ? 0 : 1, 9) . $this->numberExtension->numberBetween(0, 9);
+
+        $code = $prefix . $group . Extension\Helper::numerify(str_repeat('#', 7));
+
+        return sprintf('%s%s', $code, Calculator\Ean::checksum($code));
+    }
+
+    public function ismn(): string
+    {
+        $code = '9790' . Extension\Helper::numerify(str_repeat('#', 8));
 
         return sprintf('%s%s', $code, Calculator\Ean::checksum($code));
     }

src/Faker/Extension/BarcodeExtension.php

@@ -35,7 +35,16 @@ public function isbn10(): string;
      *
      * @see http://en.wikipedia.org/wiki/International_Standard_Book_Number
      *
-     * @example '9790404436093'
+     * @example '9791404436090'
      */
     public function isbn13(): string;
+
+    /**
+     * Get a random ISMN code
+     *
+     * @see https://en.wikipedia.org/wiki/International_Standard_Music_Number
+     *
+     * @example '9790404436093'
+     */
+    public function ismn(): string;
 }

src/Faker/Generator.php

@@ -860,13 +860,25 @@ public function isbn10(): string
      *
      * @see http://en.wikipedia.org/wiki/International_Standard_Book_Number
      *
-     * @example '9790404436093'
+     * @example '9791404436090'
      */
     public function isbn13(): string
     {
         return $this->ext(Extension\BarcodeExtension::class)->isbn13();
     }
 
+    /**
+     * Get a random ISMN code
+     *
+     * @see https://en.wikipedia.org/wiki/International_Standard_Music_Number
+     *
+     * @example '9790404436093'
+     */
+    public function ismn(): string
+    {
+        return $this->ext(Extension\BarcodeExtension::class)->ismn();
+    }
+
     /**
      * Returns a random number between $int1 and $int2 (any order)
      *

test/Faker/Core/BarcodeTest.php

@@ -34,7 +34,14 @@ public function testIsbn10(): void
     public function testIsbn13(): void
     {
         $code = $this->faker->isbn13();
-        self::assertMatchesRegularExpression('/^\d{13}$/i', $code);
+        self::assertMatchesRegularExpression('/^97(8\d{9}|9[1-9]\d{8})\d$/i', $code);
+        self::assertTrue(Ean::isValid($code));
+    }
+
+    public function testIsmn(): void
+    {
+        $code = $this->faker->ismn();
+        self::assertMatchesRegularExpression('/^9790\d{9}$/i', $code);
         self::assertTrue(Ean::isValid($code));
     }
 }