allow for zero-second durations.

Author: peccator085

src/ValueObjects/DurationValue.php

@@ -58,6 +58,10 @@ public function format(): string
             $value .= "{$this->interval->s}S";
         }
 
+        if ($value == "P" || $value == "-P") {
+            return "PT0S";
+        }
+
         return $value;
     }
 }

tests/ValueObjects/DurationValueTest.php

@@ -22,6 +22,12 @@
     assertEquals('P4DT3H2M1S', $value->format());
 });
 
+test('it can create 0 seconds duration', function () {
+    $value = DurationValue::create('PT0S');
+
+    assertEquals('PT0S', $value->format());
+});
+
 test('it can use a regular string as duration', function () {
     $value = DurationValue::create('PT5M');