1 files changed, 154 insertions, 0 deletions
diff --git a/library/core/tests/iter/adapters/intersperse.rs b/library/core/tests/iter/adapters/intersperse.rs
new file mode 100644
index 000000000..72ae59b6b
--- /dev/null
+++ b/library/core/tests/iter/adapters/intersperse.rs
@@ -0,0 +1,154 @@
+use core::iter::*;
+
+#[test]
+fn test_intersperse() {
+    let v = std::iter::empty().intersperse(0u32).collect::<Vec<_>>();
+    assert_eq!(v, vec![]);
+
+    let v = std::iter::once(1).intersperse(0).collect::<Vec<_>>();
+    assert_eq!(v, vec![1]);
+
+    let xs = ["a", "", "b", "c"];
+    let v: Vec<&str> = xs.iter().map(|x| *x).intersperse(", ").collect();
+    let text: String = v.concat();
+    assert_eq!(text, "a, , b, c".to_string());
+
+    let ys = [0, 1, 2, 3];
+    let mut it = ys[..0].iter().map(|x| *x).intersperse(1);
+    assert!(it.next() == None);
+}
+
+#[test]
+fn test_intersperse_size_hint() {
+    let iter = std::iter::empty::<i32>().intersperse(0);
+    assert_eq!(iter.size_hint(), (0, Some(0)));
+
+    let xs = ["a", "", "b", "c"];
+    let mut iter = xs.iter().map(|x| *x).intersperse(", ");
+    assert_eq!(iter.size_hint(), (7, Some(7)));
+
+    assert_eq!(iter.next(), Some("a"));
+    assert_eq!(iter.size_hint(), (6, Some(6)));
+    assert_eq!(iter.next(), Some(", "));
+    assert_eq!(iter.size_hint(), (5, Some(5)));
+
+    assert_eq!([].iter().intersperse(&()).size_hint(), (0, Some(0)));
+}
+
+#[test]
+fn test_fold_specialization_intersperse() {
+    let mut iter = (1..2).intersperse(0);
+    iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
+
+    let mut iter = (1..3).intersperse(0);
+    iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
+
+    let mut iter = (1..4).intersperse(0);
+    iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
+}
+
+#[test]
+fn test_try_fold_specialization_intersperse_ok() {
+    let mut iter = (1..2).intersperse(0);
+    iter.clone().try_for_each(|x| {
+        assert_eq!(Some(x), iter.next());
+        Some(())
+    });
+
+    let mut iter = (1..3).intersperse(0);
+    iter.clone().try_for_each(|x| {
+        assert_eq!(Some(x), iter.next());
+        Some(())
+    });
+
+    let mut iter = (1..4).intersperse(0);
+    iter.clone().try_for_each(|x| {
+        assert_eq!(Some(x), iter.next());
+        Some(())
+    });
+}
+
+#[test]
+fn test_intersperse_with() {
+    #[derive(PartialEq, Debug)]
+    struct NotClone {
+        u: u32,
+    }
+    let r = [NotClone { u: 0 }, NotClone { u: 1 }]
+        .into_iter()
+        .intersperse_with(|| NotClone { u: 2 })
+        .collect::<Vec<_>>();
+    assert_eq!(r, vec![NotClone { u: 0 }, NotClone { u: 2 }, NotClone { u: 1 }]);
+
+    let mut ctr = 100;
+    let separator = || {
+        ctr *= 2;
+        ctr
+    };
+    let r = (0..3).intersperse_with(separator).collect::<Vec<_>>();
+    assert_eq!(r, vec![0, 200, 1, 400, 2]);
+}
+
+#[test]
+fn test_intersperse_fold() {
+    let v = (1..4).intersperse(9).fold(Vec::new(), |mut acc, x| {
+        acc.push(x);
+        acc
+    });
+    assert_eq!(v.as_slice(), [1, 9, 2, 9, 3]);
+
+    let mut iter = (1..4).intersperse(9);
+    assert_eq!(iter.next(), Some(1));
+    let v = iter.fold(Vec::new(), |mut acc, x| {
+        acc.push(x);
+        acc
+    });
+    assert_eq!(v.as_slice(), [9, 2, 9, 3]);
+
+    struct NoneAtStart(i32); // Produces: None, Some(2), Some(3), None, ...
+    impl Iterator for NoneAtStart {
+        type Item = i32;
+        fn next(&mut self) -> Option<i32> {
+            self.0 += 1;
+            Some(self.0).filter(|i| i % 3 != 1)
+        }
+    }
+
+    let v = NoneAtStart(0).intersperse(1000).fold(0, |a, b| a + b);
+    assert_eq!(v, 0);
+}
+
+#[test]
+fn test_intersperse_collect_string() {
+    let contents = [1, 2, 3];
+
+    let contents_string = contents
+        .into_iter()
+        .map(|id| id.to_string())
+        .intersperse(", ".to_owned())
+        .collect::<String>();
+    assert_eq!(contents_string, "1, 2, 3");
+}
+
+#[test]
+fn test_try_fold_specialization_intersperse_err() {
+    let orig_iter = ["a", "b"].iter().copied().intersperse("-");
+
+    // Abort after the first item.
+    let mut iter = orig_iter.clone();
+    iter.try_for_each(|_| None::<()>);
+    assert_eq!(iter.next(), Some("-"));
+    assert_eq!(iter.next(), Some("b"));
+    assert_eq!(iter.next(), None);
+
+    // Abort after the second item.
+    let mut iter = orig_iter.clone();
+    iter.try_for_each(|item| if item == "-" { None } else { Some(()) });
+    assert_eq!(iter.next(), Some("b"));
+    assert_eq!(iter.next(), None);
+
+    // Abort after the third item.
+    let mut iter = orig_iter.clone();
+    iter.try_for_each(|item| if item == "b" { None } else { Some(()) });
+    assert_eq!(iter.next(), None);
+}