Remove mt_getrandmax() from WithTransaction jitter

src/Operation/WithTransaction.php

@@ -12,7 +12,6 @@
 use function floor;
 use function hrtime;
 use function min;
-use function mt_getrandmax;
 use function random_int;
 use function usleep;
 
@@ -212,10 +211,9 @@ private function getJitter(): float
             return ($this->jitterGenerator)();
         }
 
-        // Jitter is a random float from [0, 1)
-        // Since rand will return an int from 0 to mt_getrandmax(), we can divide the result by mt_getrandmax() + 1 to
-        // get a float in the range [0, 1)
-        return random_int(0, mt_getrandmax()) / (mt_getrandmax() + 1);
+        // Jitter is a random float from [0, 1]
+        // 2 ** 53 is the largest integer that can be represented in a float without losing precision
+        return random_int(0, 2 ** 53) / 2 ** 53;
     }
 
     /**

tests/Operation/WithTransactionTest.php

@@ -52,4 +52,18 @@ public function testComputeBackoffMSUsesRandom(): void
 
         $this->assertNotSame($first, $second, 'computeBackoffMs() multiplies backoff with a random value');
     }
+
+    public function testJitter(): void
+    {
+        $operation = new WithTransaction(fn () => 0);
+
+        $method = new ReflectionMethod($operation, 'getJitter');
+
+        // Test that the default jitter value is between 0 and 1
+        for ($i = 0; $i < 100; $i++) {
+            $jitter = $method->invoke($operation);
+            $this->assertGreaterThanOrEqual(0, $jitter);
+            $this->assertLessThanOrEqual(1, $jitter);
+        }
+    }
 }