Ignore encoding case in assert_xml_eq

This fixes flaky tests where encoding is either `utf-8` or `UTF-8`.

schema/src/tests/utils.rs

@@ -1,6 +1,26 @@
+use xml::reader::XmlEvent;
+
 pub fn assert_xml_eq(actual: &str, expected: &str) {
     for (a, e) in without_whitespaces(actual).zip(without_whitespaces(expected)) {
-        assert_eq!(a, e);
+        match (a, e) {
+            (
+                Ok(XmlEvent::StartDocument {
+                    version,
+                    encoding,
+                    standalone,
+                }),
+                Ok(XmlEvent::StartDocument {
+                    version: version_expected,
+                    encoding: encoding_expected,
+                    standalone: standalone_expected,
+                }),
+            ) => {
+                assert_eq!(version, version_expected);
+                assert_eq!(encoding.to_lowercase(), encoding_expected.to_lowercase());
+                assert_eq!(standalone, standalone_expected);
+            }
+            (a, e) => assert_eq!(a, e),
+        }
     }
 }