Fix parse() negative number bug, add tests

src/BigInteger.php

@@ -110,9 +110,9 @@ public static function parse(string $number, int $base = 10) : BigInteger
             return new BigInteger($sign . $number);
         }
 
-        $result = Calculator::get()->fromBase($sign . $number, $base);
+        $result = Calculator::get()->fromBase($number, $base);
 
-        return new BigInteger($result);
+        return new BigInteger($sign . $result);
     }
 
     /**

src/Internal/Calculator.php

@@ -276,8 +276,7 @@ public function gcd(string $a, string $b) : string
      * This method can be overridden by the concrete implementation if the underlying library
      * has built-in support for base conversion.
      *
-     * @param string $number The number, non-empty, case-insensitively validated for the given base.
-     *                       The number may contain an optional leading + or - sign, and optional leading zeros.
+     * @param string $number The number, positive or zero, non-empty, case-insensitively validated for the given base.
      * @param int    $base   The base of the number, validated from 2 to 36.
      *
      * @return string The converted number, following the Calculator conventions.

tests/BigIntegerTest.php

@@ -184,6 +184,13 @@ public function providerParse()
             ['+0456', 10, '456'],
             ['-0789', 10, '-789'],
 
+            ['123', 11, '146'],
+            ['+456', 11, '545'],
+            ['-789', 11, '-944'],
+            ['0123', 11, '146'],
+            ['+0456', 11, '545'],
+            ['-0789', 11, '-944'],
+
             ['110011001100110011001111', 36, '640998479760579495168036691627608949'],
             ['110011001100110011001111', 35, '335582856048758779730579523833856636'],
             ['110011001100110011001111', 34, '172426711023004493064981145981549295'],