fluent-iterable 1.0.1

Fluent extension trait for std Iterator, port of @codibre/fluent-iterable vocabulary: joins, grouping, distinctness, cardinality checks
Documentation 
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// Tests for the fallback family (spliced into `lib.rs`'s test module).

    #[test]
    fn repeat_of_empty_source_is_empty() {
        let out: Vec<i32> = std::iter::empty::<i32>().repeat(4).collect();
        assert!(out.is_empty());
    }


    #[test]
    fn repeat_replays_whole_sequence() {
        let out: Vec<i32> = [1, 2].into_iter().repeat(3).collect();
        assert_eq!(out, vec![1, 2, 1, 2, 1, 2]);
        let out: Vec<i32> = [1, 2].into_iter().repeat(1).collect();
        assert_eq!(out, vec![1, 2]);
    }


    #[test]
    fn repeat_streams_first_pass_before_replaying() {
        let (source, counter) = counting([1, 2, 3].into_iter());
        let mut rep = source.repeat(2);
        assert_eq!(rep.next(), Some(1));
        // only one item pulled so far: the first pass is streaming
        assert_eq!(counter.get(), 1);
        assert_eq!(rep.next(), Some(2));
        assert_eq!(rep.next(), Some(3));
        assert_eq!(rep.next(), Some(1)); // replay started
        assert_eq!(rep.count(), 2);
    }


    #[test]
    fn repeat_zero_never_consumes_source() {
        let (source, counter) = counting([1, 2, 3].into_iter());
        let out: Vec<i32> = source.repeat(0).collect();
        assert!(out.is_empty());
        assert_eq!(counter.get(), 0);
    }


    #[test]
    fn when_empty_falls_back_after_late_first_value_absent() {
        // source yields nothing but is polled several times before giving up
        let (source, counter) = counting(std::iter::empty::<i32>());
        let out: Vec<i32> = source.when_empty([9]).collect();
        assert_eq!(out, vec![9]);
        assert_eq!(counter.get(), 0);
    }


    #[test]
    fn when_empty_uses_fallback_only_for_empty_source() {
        let empty: [i32; 0] = [];
        let out: Vec<i32> = empty.into_iter().when_empty([7, 8]).collect();
        assert_eq!(out, vec![7, 8]);

        let (fallback_source, fallback_counter) = counting([7, 8].into_iter());
        let out: Vec<i32> = [1, 2].into_iter().when_empty(fallback_source).collect();
        assert_eq!(out, vec![1, 2]);
        assert_eq!(fallback_counter.get(), 0, "fallback must stay untouched");
    }


    #[test]
    fn when_empty_with_empty_fallback_is_empty() {
        let empty: [i32; 0] = [];
        let out: Vec<i32> = empty.into_iter().when_empty(empty).collect();
        assert!(out.is_empty());
    }