Add test cases that better indicate null behavior

Signed-off-by: Luc Perkins <[email protected]>

lib/remap-functions/src/del.rs

@@ -28,6 +28,13 @@ pub struct DelFn {
     field: Path,
 }
 
+impl DelFn {
+    #[cfg(test)]
+    fn new(field: Path) -> Self {
+        Self { field }
+    }
+}
+
 impl Expression for DelFn {
     fn execute(&self, _: &mut state::Program, object: &mut dyn Object) -> Result<Value> {
         match object.remove(self.field.as_ref(), false) {
@@ -50,24 +57,47 @@ impl Expression for DelFn {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::map;
 
-    test_type_def![static_type_def {
-        expr: |_| DelFn {
-            field: Path::from("foo"),
-        },
-        def: TypeDef {
-            fallible: true,
-            kind: value::Kind::Null,
-            ..Default::default()
-        },
-    }];
+    test_type_def![
+        static_type_def {
+            expr: |_| DelFn {
+                field: Path::from("foo"),
+            },
+            def: TypeDef {
+                fallible: true,
+                kind: value::Kind::Null,
+                ..Default::default()
+            },
+        }
+    ];
+
+    #[test]
+    fn del() {
+        let cases = vec![
+            (
+                // Delete existing field
+                map!["exists": "value"],
+                Ok(Value::Null),
+                DelFn::new(Path::from("exists")),
+            ),
+            (
+                // Delete non-existing field
+                map!["exists": "value"],
+                Ok(Value::Null),
+                DelFn::new(Path::from("does_not_exist")),
+            )
+        ];
+
+        let mut state = state::Program::default();
 
-    test_function![
-        del => Del;
+        for (object, exp, func) in cases {
+            let mut object: Value = object.into();
+            let got = func
+                .execute(&mut state, &mut object)
+                .map_err(|e| format!("{:#}", anyhow::anyhow!(e)));
 
-        array {
-            args: func_args![field: Path::from("foo")],
-            want: Ok(value!(null)),
+            assert_eq!(got, exp);
         }
-    ];
+    }
 }