1 files changed, 13 insertions, 2 deletions
diff --git a/tests/test_spans.rs b/tests/test_spans.rs
index e839f53..28342ea 100644
--- a/tests/test_spans.rs
+++ b/tests/test_spans.rs
@@ -213,9 +213,20 @@ fn doctype_id_spans() {
 fn annotate_errors(html: &'static str) -> String {
     let mut labels = Vec::new();
     for token in tokenizer(html) {
-        if let Token::Error { error, span } = token {
-            labels.push((span, error.code()));
+        let Token::Error { error, span } = token else {
+            continue;
+        };
+
+        if span.start == span.end {
+            if span.start != html.len() {
+                panic!("empty error spans are only allowed at the very end of the source (for eof errors)");
+            }
+        } else {
+            assert!(span.start < span.end);
+            assert!(span.end <= html.len());
         }
+
+        labels.push((span, error.code()));
     }
     annotate(html, labels)
 }