Added more tests (#1103)

tests/it/array/utf8/to_mutable.rs

@@ -1,14 +1,67 @@
-use arrow2::array::Utf8Array;
+use arrow2::{array::Utf8Array, bitmap::Bitmap, buffer::Buffer, datatypes::DataType};
 
 #[test]
-#[allow(clippy::redundant_clone)]
-fn array_to_mutable() {
+fn not_shared() {
     let array = Utf8Array::<i32>::from(&[Some("hello"), Some(" "), None]);
-    let mutable = array.into_mut().unwrap_right();
+    assert!(array.into_mut().is_right());
+}
+
+#[test]
+#[allow(clippy::redundant_clone)]
+fn shared_validity() {
+    let validity = Bitmap::from([true]);
+    let array = Utf8Array::<i32>::new(
+        DataType::Utf8,
+        vec![0, 1].into(),
+        b"a".to_vec().into(),
+        Some(validity.clone()),
+    );
+    assert!(array.into_mut().is_left())
+}
 
-    let array: Utf8Array<i32> = mutable.into();
-    let array2 = array.clone();
-    let maybe_mut = array2.into_mut();
-    // the ref count is 2 we should not get a mutable.
-    assert!(maybe_mut.is_left())
+#[test]
+#[allow(clippy::redundant_clone)]
+fn shared_values() {
+    let values: Buffer<u8> = b"a".to_vec().into();
+    let array = Utf8Array::<i32>::new(
+        DataType::Utf8,
+        vec![0, 1].into(),
+        values.clone(),
+        Some(Bitmap::from([true])),
+    );
+    assert!(array.into_mut().is_left())
+}
+
+#[test]
+#[allow(clippy::redundant_clone)]
+fn shared_offsets_values() {
+    let offsets: Buffer<i32> = vec![0, 1].into();
+    let values: Buffer<u8> = b"a".to_vec().into();
+    let array = Utf8Array::<i32>::new(
+        DataType::Utf8,
+        offsets.clone(),
+        values.clone(),
+        Some(Bitmap::from([true])),
+    );
+    assert!(array.into_mut().is_left())
+}
+
+#[test]
+#[allow(clippy::redundant_clone)]
+fn shared_offsets() {
+    let offsets: Buffer<i32> = vec![0, 1].into();
+    let array = Utf8Array::<i32>::new(
+        DataType::Utf8,
+        offsets.clone(),
+        b"a".to_vec().into(),
+        Some(Bitmap::from([true])),
+    );
+    assert!(array.into_mut().is_left())
+}
+
+#[test]
+#[allow(clippy::redundant_clone)]
+fn shared_all() {
+    let array = Utf8Array::<i32>::from(&[Some("hello"), Some(" "), None]);
+    assert!(array.clone().into_mut().is_left())
 }