Add tests for BigNumber::of()

Author: BenMorel

tests/BigDecimalTest.php

@@ -72,6 +72,9 @@ public function providerOf() : array
             ['+.2', '2', 1],
             ['-.33', '-33', 2],
             ['1.e2', '100', 0],
+            ['.1e-1', '1', 2],
+            ['.1e0', '1', 1],
+            ['.1e1', '1', 0],
             ['.1e2', '10', 0],
             ['1.e-2', '1', 2],
             ['.1e-2', '1', 3],