1 files changed, 106 insertions, 0 deletions
diff --git a/src/iter/find_first_last/test.rs b/src/iter/find_first_last/test.rs
new file mode 100644
index 0000000..05271bc
--- /dev/null
+++ b/src/iter/find_first_last/test.rs
@@ -0,0 +1,106 @@
+use super::*;
+use std::sync::atomic::AtomicUsize;
+
+#[test]
+fn same_range_first_consumers_return_correct_answer() {
+    let find_op = |x: &i32| x % 2 == 0;
+    let first_found = AtomicUsize::new(usize::max_value());
+    let far_right_consumer = FindConsumer::new(&find_op, MatchPosition::Leftmost, &first_found);
+
+    // We save a consumer that will be far to the right of the main consumer (and therefore not
+    // sharing an index range with that consumer) for fullness testing
+    let consumer = far_right_consumer.split_off_left();
+
+    // split until we have an indivisible range
+    let bits_in_usize = usize::min_value().count_zeros();
+
+    for _ in 0..bits_in_usize {
+        consumer.split_off_left();
+    }
+
+    let reducer = consumer.to_reducer();
+    // the left and right folders should now have the same range, having
+    // exhausted the resolution of usize
+    let left_folder = consumer.split_off_left().into_folder();
+    let right_folder = consumer.into_folder();
+
+    let left_folder = left_folder.consume(0).consume(1);
+    assert_eq!(left_folder.boundary, right_folder.boundary);
+    // expect not full even though a better match has been found because the
+    // ranges are the same
+    assert!(!right_folder.full());
+    assert!(far_right_consumer.full());
+    let right_folder = right_folder.consume(2).consume(3);
+    assert_eq!(
+        reducer.reduce(left_folder.complete(), right_folder.complete()),
+        Some(0)
+    );
+}
+
+#[test]
+fn same_range_last_consumers_return_correct_answer() {
+    let find_op = |x: &i32| x % 2 == 0;
+    let last_found = AtomicUsize::new(0);
+    let consumer = FindConsumer::new(&find_op, MatchPosition::Rightmost, &last_found);
+
+    // We save a consumer that will be far to the left of the main consumer (and therefore not
+    // sharing an index range with that consumer) for fullness testing
+    let far_left_consumer = consumer.split_off_left();
+
+    // split until we have an indivisible range
+    let bits_in_usize = usize::min_value().count_zeros();
+    for _ in 0..bits_in_usize {
+        consumer.split_off_left();
+    }
+
+    let reducer = consumer.to_reducer();
+    // due to the exact calculation in split_off_left, the very last consumer has a
+    // range of width 2, so we use the second-to-last consumer instead to get
+    // the same boundary on both folders
+    let consumer = consumer.split_off_left();
+    let left_folder = consumer.split_off_left().into_folder();
+    let right_folder = consumer.into_folder();
+    let right_folder = right_folder.consume(2).consume(3);
+    assert_eq!(left_folder.boundary, right_folder.boundary);
+    // expect not full even though a better match has been found because the
+    // ranges are the same
+    assert!(!left_folder.full());
+    assert!(far_left_consumer.full());
+    let left_folder = left_folder.consume(0).consume(1);
+    assert_eq!(
+        reducer.reduce(left_folder.complete(), right_folder.complete()),
+        Some(2)
+    );
+}
+
+// These tests requires that a folder be assigned to an iterator with more than
+// one element. We can't necessarily determine when that will happen for a given
+// input to find_first/find_last, so we test the folder directly here instead.
+#[test]
+fn find_first_folder_does_not_clobber_first_found() {
+    let best_found = AtomicUsize::new(usize::max_value());
+    let f = FindFolder {
+        find_op: &(|&_: &i32| -> bool { true }),
+        boundary: 0,
+        match_position: MatchPosition::Leftmost,
+        best_found: &best_found,
+        item: None,
+    };
+    let f = f.consume(0_i32).consume(1_i32).consume(2_i32);
+    assert!(f.full());
+    assert_eq!(f.complete(), Some(0_i32));
+}
+
+#[test]
+fn find_last_folder_yields_last_match() {
+    let best_found = AtomicUsize::new(0);
+    let f = FindFolder {
+        find_op: &(|&_: &i32| -> bool { true }),
+        boundary: 0,
+        match_position: MatchPosition::Rightmost,
+        best_found: &best_found,
+        item: None,
+    };
+    let f = f.consume(0_i32).consume(1_i32).consume(2_i32);
+    assert_eq!(f.complete(), Some(2_i32));
+}