add the two test cases for the OTPResult struct

Author: tmthecoder

tests/otp_result.rs

@@ -0,0 +1,13 @@
+use xotp::otp_result::OTPResult;
+
+#[test]
+fn test_padding_needed() {
+    let result = OTPResult::new(6, 1234);
+    assert_eq!("001234", result.as_string())
+}
+
+#[test]
+fn test_padding_not_needed() {
+    let result = OTPResult::new(6, 123456);
+    assert_eq!("123456", result.as_string())
+}