diff --git a/src/lib.rs b/src/lib.rs
index ed1bbbee..8a785544 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -36,8 +36,16 @@ impl<'a> JsonAta<'a> {
         self.frame.bind(name, value)
     }
 
-    pub fn register_function(&self, name: &str, arity: usize, implementation: fn(FunctionContext<'a, '_>, &'a Value<'a>) -> Result<&'a Value<'a>>) {
-        self.frame.bind(name, Value::nativefn(&self.arena, name, arity, implementation));
+    pub fn register_function(
+        &self,
+        name: &str,
+        arity: usize,
+        implementation: fn(FunctionContext<'a, '_>, &'a Value<'a>) -> Result<&'a Value<'a>>,
+    ) {
+        self.frame.bind(
+            name,
+            Value::nativefn(self.arena, name, arity, implementation),
+        );
     }
 
     pub fn evaluate(&self, input: Option<&str>) -> Result<&'a Value<'a>> {
@@ -112,7 +120,7 @@ impl<'a> JsonAta<'a> {
 }
 
 #[cfg(test)]
-mod tests{
+mod tests {
     use super::*;
 
     #[test]
@@ -120,7 +128,7 @@ mod tests{
         let arena = Bump::new();
         let jsonata = JsonAta::new("$test()", &arena).unwrap();
         jsonata.register_function("test", 0, |ctx, _| Ok(Value::number(ctx.arena, 1)));
-        
+
         let result = jsonata.evaluate(Some(r#"anything"#));
 
         assert_eq!(result.unwrap(), Value::number(&arena, 1));
@@ -130,8 +138,10 @@ mod tests{
     fn register_function_override_now() {
         let arena = Bump::new();
         let jsonata = JsonAta::new("$now()", &arena).unwrap();
-        jsonata.register_function("now", 0, |ctx, _| Ok(Value::string(ctx.arena, "time for tea")));
-        
+        jsonata.register_function("now", 0, |ctx, _| {
+            Ok(Value::string(ctx.arena, "time for tea"))
+        });
+
         let result = jsonata.evaluate(Some(r#"anything"#));
 
         assert_eq!(result.unwrap(), Value::string(&arena, "time for tea"));
@@ -143,12 +153,19 @@ mod tests{
         let jsonata = JsonAta::new("$map([1,4,9,16], $squareroot)", &arena).unwrap();
         jsonata.register_function("squareroot", 1, |ctx, args| {
             let num = &args[0];
-            return Ok(Value::number(ctx.arena, (num.as_f64()).sqrt()))
+            return Ok(Value::number(ctx.arena, (num.as_f64()).sqrt()));
         });
-        
+
         let result = jsonata.evaluate(Some(r#"anything"#));
 
-        assert_eq!(result.unwrap().members().map(|v| v.as_f64()).collect::<Vec<f64>>(), vec![1.0, 2.0, 3.0, 4.0]);
+        assert_eq!(
+            result
+                .unwrap()
+                .members()
+                .map(|v| v.as_f64())
+                .collect::<Vec<f64>>(),
+            vec![1.0, 2.0, 3.0, 4.0]
+        );
     }
 
     #[test]
@@ -159,9 +176,16 @@ mod tests{
             let num = &args[0];
             return Ok(Value::bool(ctx.arena, (num.as_f64()) % 2.0 == 0.0));
         });
-        
+
         let result = jsonata.evaluate(Some(r#"anything"#));
 
-        assert_eq!(result.unwrap().members().map(|v| v.as_f64()).collect::<Vec<f64>>(), vec![4.0, 16.0]);
+        assert_eq!(
+            result
+                .unwrap()
+                .members()
+                .map(|v| v.as_f64())
+                .collect::<Vec<f64>>(),
+            vec![4.0, 16.0]
+        );
     }
 }