diff --git a/src/pretty_print.rs b/src/pretty_print.rs
index 625283f8..9768a667 100644
--- a/src/pretty_print.rs
+++ b/src/pretty_print.rs
@@ -513,3 +513,200 @@ fn need_quotes(string: &str) -> bool {
         || string.parse::<i64>().is_ok()
         || string.parse::<f64>().is_ok()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use sxd_document::dom::{ChildOfElement, ChildOfRoot};
+    use sxd_document::parser;
+
+    /// helper function
+    fn first_element(package: &sxd_document::Package) -> Element<'_> {
+        let doc = package.as_document();
+        for child in doc.root().children() {
+            if let ChildOfRoot::Element(e) = child {
+                return e;
+            }
+        }
+        panic!("No root element found");
+    }
+
+    #[test]
+    /// Escapes XML entities and invisible characters for safe display.
+    /// Tests the method on a few hardcoded characters.
+    fn handle_special_chars_escapes() {
+        let input = "& < > \" ' \u{2061} \u{2062} \u{2063} \u{2064} x";
+        let expected = "&amp; &lt; &gt; &quot; &apos; &#x2061; &#x2062; &#x2063; &#x2064; x";
+        assert_eq!(handle_special_chars(input), expected);
+    }
+
+    #[test]
+    /// Formats a leaf element as a single line with escaped text.
+    fn format_element_leaf_text() {
+        let package = parser::parse("<math><mi>&amp;</mi></math>").unwrap();
+        let math = first_element(&package);
+        let mi = math
+            .children()
+            .iter()
+            .find_map(|c| match c {
+                ChildOfElement::Element(e) => Some(*e),
+                _ => None,
+            })
+            .unwrap();
+        assert_eq!(format_element(mi, 0), " <mi>&amp;</mi>\n");
+    }
+
+    #[test]
+    /// Formats a nested element with indentation and newlines.
+    fn format_element_nested() {
+        let package = parser::parse("<math><mi>x</mi><mo>+</mo></math>").unwrap();
+        let math = first_element(&package);
+        let rendered = format_element(math, 0);
+        assert!(rendered.starts_with(" <math>\n"));
+        assert!(rendered.contains("\n  <mi>x</mi>\n"));
+        assert!(rendered.contains("\n  <mo>+</mo>\n"));
+        assert!(rendered.ends_with("</math>\n"));
+    }
+
+    #[test]
+    /// Escapes special characters in attribute values.
+    fn format_attrs_escapes() {
+        let package = parser::parse("<math a=\"&amp;\" b=\"&lt;\"></math>").unwrap();
+        let math = first_element(&package);
+        let rendered = format_attrs(&math.attributes());
+        assert!(rendered.contains(" a='&amp;'"));
+        assert!(rendered.contains(" b='&lt;'"));
+    }
+
+    #[test]
+    /// Preserves non-BMP characters from a literal XML form.
+    fn format_element_non_bmp_character_literal() {
+        let package = parser::parse("<math><mi>𝞪</mi></math>").unwrap();
+        let math = first_element(&package);
+        let mi = math
+            .children()
+            .iter()
+            .find_map(|c| match c {
+                ChildOfElement::Element(e) => Some(*e),
+                _ => None,
+            })
+            .unwrap();
+        let rendered = format_element(mi, 0);
+        assert!(rendered.contains("𝞪"));
+    }
+
+    #[test]
+    /// Preserves non-BMP characters from a numeric XML form.
+    fn format_element_non_bmp_character_numeric() {
+        let package = parser::parse("<math><mi>&#x1d7aa;</mi></math>").unwrap();
+        let math = first_element(&package);
+        let mi = math
+            .children()
+            .iter()
+            .find_map(|c| match c {
+                ChildOfElement::Element(e) => Some(*e),
+                _ => None,
+            })
+            .unwrap();
+        let rendered = format_element(mi, 0);
+        assert!(rendered.contains("𝞪"));
+    }
+
+    #[test]
+    /// Evaluates non-BMP literal text through sxd_xpath.
+    fn xpath_non_bmp_literal() {
+        use sxd_xpath::{Factory, Value};
+
+        let package = parser::parse("<math><mi>𝞪</mi></math>").unwrap();
+        let xpath = Factory::new().build("string(/math/mi)").unwrap().unwrap();
+        let context = sxd_xpath::Context::new();
+
+        let value = xpath.evaluate(&context, first_element(&package)).unwrap();
+        match value {
+            Value::String(s) => assert_eq!(s, "𝞪"),
+            _ => panic!("Expected string value from xpath"),
+        }
+    }
+
+    #[test]
+    /// Evaluates non-BMP numeric text through sxd_xpath.
+    fn xpath_non_bmp_numeric() {
+        use sxd_xpath::{Factory, Value};
+
+        let package = parser::parse("<math><mi>&#x1d7aa;</mi></math>").unwrap();
+        let xpath = Factory::new().build("string(/math/mi)").unwrap().unwrap();
+        let context = sxd_xpath::Context::new();
+
+        let value = xpath.evaluate(&context, first_element(&package)).unwrap();
+        match value {
+            Value::String(s) => assert_eq!(s, "𝞪"),
+            _ => panic!("Expected string value from xpath"),
+        }
+    }
+
+    #[test]
+    /// Evaluates non-BMP literal text with a MathML namespace-qualified XPath.
+    fn xpath_non_bmp_namespace_literal() {
+        use sxd_xpath::{Factory, Value};
+
+        let xml = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>𝞪</mi></math>";
+        let package = parser::parse(xml).unwrap();
+        let xpath = Factory::new()
+            .build("string(/m:math/m:mi)")
+            .unwrap()
+            .unwrap();
+        let mut context = sxd_xpath::Context::new();
+        context.set_namespace("m", "http://www.w3.org/1998/Math/MathML");
+
+        let value = xpath.evaluate(&context, first_element(&package)).unwrap();
+        match value {
+            Value::String(s) => assert_eq!(s, "𝞪"),
+            _ => panic!("Expected string value from xpath"),
+        }
+    }
+
+    #[test]
+    /// Evaluates non-BMP numeric text with a MathML namespace-qualified XPath.
+    fn xpath_non_bmp_namespace_numeric() {
+        use sxd_xpath::{Factory, Value};
+
+        let xml = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>&#120746;</mi></math>";
+        let package = parser::parse(xml).unwrap();
+        let xpath = Factory::new()
+            .build("string(/m:math/m:mi)")
+            .unwrap()
+            .unwrap();
+        let mut context = sxd_xpath::Context::new();
+        context.set_namespace("m", "http://www.w3.org/1998/Math/MathML");
+
+        let value = xpath.evaluate(&context, first_element(&package)).unwrap();
+        match value {
+            Value::String(s) => assert_eq!(s, "𝞪"),
+            _ => panic!("Expected string value from xpath"),
+        }
+    }
+
+    #[test]
+    /// Extracts a text node via XPath (nodeset result) and verifies the non-BMP character survives.
+    fn xpath_non_bmp_text_nodeset() {
+        use sxd_xpath::{Factory, Value};
+
+        let xml = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>𝞪</mi></math>";
+        let package = parser::parse(xml).unwrap();
+        let xpath = Factory::new().build("/m:math/m:mi/text()").unwrap().unwrap();
+        let mut context = sxd_xpath::Context::new();
+        context.set_namespace("m", "http://www.w3.org/1998/Math/MathML");
+
+        let value = xpath.evaluate(&context, first_element(&package)).unwrap();
+        match value {
+            Value::Nodeset(nodes) => {
+                let ordered = nodes.document_order();
+                let node = ordered.first().expect("Expected one text node");
+                let text = node.text().expect("Expected text node");
+                assert_eq!(text.text(), "𝞪");
+                assert_eq!(ordered.len(), 1);
+            }
+            _ => panic!("Expected nodeset value from xpath"),
+        }
+    }
+}