Add negative trivial tests

We should ensure, that incorrect input do not deserializing into object.
That could influence untagged enums because thy rely on deserialization
failures when selects right variant

failures (38):
    trivial::struct_::cdata::byte_buf
    trivial::struct_::cdata::char_
    trivial::struct_::cdata::f32_
    trivial::struct_::cdata::f64_
    trivial::struct_::cdata::false_
    trivial::struct_::cdata::i128_
    trivial::struct_::cdata::i16_
    trivial::struct_::cdata::i32_
    trivial::struct_::cdata::i64_
    trivial::struct_::cdata::i8_
    trivial::struct_::cdata::isize_
    trivial::struct_::cdata::string
    trivial::struct_::cdata::true_
    trivial::struct_::cdata::u128_
    trivial::struct_::cdata::u16_
    trivial::struct_::cdata::u32_
    trivial::struct_::cdata::u64_
    trivial::struct_::cdata::u8_
    trivial::struct_::cdata::usize_
    trivial::struct_::text::byte_buf
    trivial::struct_::text::char_
    trivial::struct_::text::f32_
    trivial::struct_::text::f64_
    trivial::struct_::text::false_
    trivial::struct_::text::i128_
    trivial::struct_::text::i16_
    trivial::struct_::text::i32_
    trivial::struct_::text::i64_
    trivial::struct_::text::i8_
    trivial::struct_::text::isize_
    trivial::struct_::text::string
    trivial::struct_::text::true_
    trivial::struct_::text::u128_
    trivial::struct_::text::u16_
    trivial::struct_::text::u32_
    trivial::struct_::text::u64_
    trivial::struct_::text::u8_
    trivial::struct_::text::usize_

Author: Mingun

Changelog.md

@@ -26,7 +26,12 @@
   |`DeError::EndOfAttributes`|Renamed to `DeError::KeyNotFound`
   |`DeError::ExpectedStart`|Added
 
+### New Tests
+
+- [#9]: Added tests for incorrect nested tags in input
+
 [#8]: https://github.com/Mingun/fast-xml/pull/8
+[#9]: https://github.com/Mingun/fast-xml/pull/9
 
 ## 0.23.0 -- 2022-05-08
 

tests/serde-de.rs

@@ -316,6 +316,15 @@ mod trivial {
                     let item: Trivial<$type> = from_str($value).unwrap();
 
                     assert_eq!(item, Trivial { value: $expected });
+
+                    match from_str::<Trivial<$type>>(&format!("<outer>{}</outer>", $value)) {
+                        // Expected unexpected start element `<root>`
+                        Err(DeError::UnexpectedStart(tag)) => assert_eq!(tag, b"root"),
+                        x => panic!(
+                            r#"Expected `Err(DeError::UnexpectedStart("root"))`, but got `{:?}`"#,
+                            x
+                        ),
+                    }
                 }
             };
         }