1 files changed, 148 insertions, 0 deletions
diff --git a/library/core/tests/iter/adapters/take.rs b/library/core/tests/iter/adapters/take.rs
new file mode 100644
index 000000000..bfb659f0a
--- /dev/null
+++ b/library/core/tests/iter/adapters/take.rs
@@ -0,0 +1,148 @@
+use core::iter::*;
+
+#[test]
+fn test_iterator_take() {
+    let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
+    let ys = [0, 1, 2, 3, 5];
+
+    let mut it = xs.iter().take(ys.len());
+    let mut i = 0;
+    assert_eq!(it.len(), ys.len());
+    while let Some(&x) = it.next() {
+        assert_eq!(x, ys[i]);
+        i += 1;
+        assert_eq!(it.len(), ys.len() - i);
+    }
+    assert_eq!(i, ys.len());
+    assert_eq!(it.len(), 0);
+
+    let mut it = xs.iter().take(ys.len());
+    let mut i = 0;
+    assert_eq!(it.len(), ys.len());
+    while let Some(&x) = it.next_back() {
+        i += 1;
+        assert_eq!(x, ys[ys.len() - i]);
+        assert_eq!(it.len(), ys.len() - i);
+    }
+    assert_eq!(i, ys.len());
+    assert_eq!(it.len(), 0);
+}
+
+#[test]
+fn test_iterator_take_nth() {
+    let xs = [0, 1, 2, 4, 5];
+    let mut it = xs.iter();
+    {
+        let mut take = it.by_ref().take(3);
+        let mut i = 0;
+        while let Some(&x) = take.nth(0) {
+            assert_eq!(x, i);
+            i += 1;
+        }
+    }
+    assert_eq!(it.nth(1), Some(&5));
+    assert_eq!(it.nth(0), None);
+
+    let xs = [0, 1, 2, 3, 4];
+    let mut it = xs.iter().take(7);
+    let mut i = 1;
+    while let Some(&x) = it.nth(1) {
+        assert_eq!(x, i);
+        i += 2;
+    }
+}
+
+#[test]
+fn test_iterator_take_nth_back() {
+    let xs = [0, 1, 2, 4, 5];
+    let mut it = xs.iter();
+    {
+        let mut take = it.by_ref().take(3);
+        let mut i = 0;
+        while let Some(&x) = take.nth_back(0) {
+            i += 1;
+            assert_eq!(x, 3 - i);
+        }
+    }
+    assert_eq!(it.nth_back(0), None);
+
+    let xs = [0, 1, 2, 3, 4];
+    let mut it = xs.iter().take(7);
+    assert_eq!(it.nth_back(1), Some(&3));
+    assert_eq!(it.nth_back(1), Some(&1));
+    assert_eq!(it.nth_back(1), None);
+}
+
+#[test]
+fn test_take_advance_by() {
+    let mut take = (0..10).take(3);
+    assert_eq!(take.advance_by(2), Ok(()));
+    assert_eq!(take.next(), Some(2));
+    assert_eq!(take.advance_by(1), Err(0));
+
+    assert_eq!((0..0).take(10).advance_by(0), Ok(()));
+    assert_eq!((0..0).take(10).advance_by(1), Err(0));
+    assert_eq!((0..10).take(4).advance_by(5), Err(4));
+
+    let mut take = (0..10).take(3);
+    assert_eq!(take.advance_back_by(2), Ok(()));
+    assert_eq!(take.next(), Some(0));
+    assert_eq!(take.advance_back_by(1), Err(0));
+
+    assert_eq!((0..2).take(1).advance_back_by(10), Err(1));
+    assert_eq!((0..0).take(1).advance_back_by(1), Err(0));
+    assert_eq!((0..0).take(1).advance_back_by(0), Ok(()));
+    assert_eq!((0..usize::MAX).take(100).advance_back_by(usize::MAX), Err(100));
+}
+
+#[test]
+fn test_iterator_take_short() {
+    let xs = [0, 1, 2, 3];
+
+    let mut it = xs.iter().take(5);
+    let mut i = 0;
+    assert_eq!(it.len(), xs.len());
+    while let Some(&x) = it.next() {
+        assert_eq!(x, xs[i]);
+        i += 1;
+        assert_eq!(it.len(), xs.len() - i);
+    }
+    assert_eq!(i, xs.len());
+    assert_eq!(it.len(), 0);
+
+    let mut it = xs.iter().take(5);
+    let mut i = 0;
+    assert_eq!(it.len(), xs.len());
+    while let Some(&x) = it.next_back() {
+        i += 1;
+        assert_eq!(x, xs[xs.len() - i]);
+        assert_eq!(it.len(), xs.len() - i);
+    }
+    assert_eq!(i, xs.len());
+    assert_eq!(it.len(), 0);
+}
+
+#[test]
+fn test_take_try_folds() {
+    let f = &|acc, x| i32::checked_add(2 * acc, x);
+    assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
+    assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
+
+    let mut iter = (10..30).take(20);
+    assert_eq!(iter.try_fold(0, i8::checked_add), None);
+    assert_eq!(iter.next(), Some(20));
+    assert_eq!(iter.try_rfold(0, i8::checked_add), None);
+    assert_eq!(iter.next_back(), Some(24));
+
+    let mut iter = (2..20).take(3);
+    assert_eq!(iter.try_for_each(Err), Err(2));
+    assert_eq!(iter.try_for_each(Err), Err(3));
+    assert_eq!(iter.try_for_each(Err), Err(4));
+    assert_eq!(iter.try_for_each(Err), Ok(()));
+
+    let mut iter = (2..20).take(3).rev();
+    assert_eq!(iter.try_for_each(Err), Err(4));
+    assert_eq!(iter.try_for_each(Err), Err(3));
+    assert_eq!(iter.try_for_each(Err), Err(2));
+    assert_eq!(iter.try_for_each(Err), Ok(()));
+}