feat(tests): enhance dictionary array tests with raw values extraction

- Added `AsArray` import for `DictionaryArray` to facilitate raw values extraction.
- Updated tests to include assertions for raw minimum values from the dictionary array, improving test coverage and validation accuracy.

Author: kosiew

datafusion/functions-aggregate-common/src/min_max.rs

@@ -911,7 +911,7 @@ pub fn max_batch(values: &ArrayRef) -> Result<ScalarValue> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use arrow::array::DictionaryArray;
+    use arrow::array::{AsArray, DictionaryArray};
     use std::sync::Arc;
 
     #[test]
@@ -997,6 +997,8 @@ mod tests {
         let keys = Int8Array::from(vec![Some(1), None, Some(1), Some(1)]);
         let values = Arc::new(StringArray::from(vec!["zzz", "bbb", "aaa"]));
         let array = Arc::new(DictionaryArray::new(keys, values)) as ArrayRef;
+        let raw_values = array.as_any_dictionary().values();
+        let raw_min = min_batch(raw_values)?;
 
         let min = min_batch(&array)?;
         let max = max_batch(&array)?;
@@ -1006,6 +1008,8 @@ mod tests {
             Box::new(ScalarValue::Utf8(Some("bbb".to_string()))),
         );
 
+        assert_ne!(raw_min, expected);
+
         assert_eq!(min, expected);
         assert_eq!(max, expected);