Added more tests.

tests/it/array/utf8/mod.rs

@@ -116,6 +116,14 @@ fn not_utf8() {
     Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
 }
 
+#[test]
+#[should_panic]
+fn not_utf8_individually() {
+    let offsets = Buffer::from(&[0, 1, 2]);
+    let values = Buffer::from([207, 128]); // each is invalid utf8, but together is valid
+    Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
+}
+
 #[test]
 #[should_panic]
 fn wrong_offsets() {
@@ -134,15 +142,27 @@ fn wrong_data_type() {
 
 #[test]
 #[should_panic]
-fn value_with_wrong_offsets_panics() {
-    let offsets = Buffer::from(&[0, 10, 11, 4]);
+fn value_with_out_of_bounds_offsets_panics() {
+    // the 10-11 is out of bounds
+    let offsets = Buffer::from(&[0, 10, 4]);
     let values = Buffer::from(b"abbb");
-    // the 10-11 is not checked
-    let array = Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
+    let _ = Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
+}
 
-    // but access is still checked (and panics)
-    // without checks, this would result in reading beyond bounds
-    array.value(0);
+#[test]
+#[should_panic]
+fn value_with_wrong_decreasing_offset_panics() {
+    let offsets = Buffer::from(&[0, 2, 1]);
+    let values = Buffer::from(b"abbb");
+    let _ = Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
+}
+
+#[test]
+#[should_panic]
+fn value_with_wrong_decreasing_offset_and_utf8_panics() {
+    let offsets = Buffer::from(&[0, 4, 2]); // not increasing
+    let values = Buffer::from([207, 128, 207, 128, 207, 128]); // valid utf8
+    let _ = Utf8Array::<i32>::from_data(DataType::Utf8, offsets, values, None);
 }
 
 #[test]