Implement quickcheck::Arbitrary for Weekday

emlun · Oct 25, 2020 · adefde0 · adefde0
1 parent bc43ce2
commit adefde0
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diff --git a/src/quickcheck.rs b/src/quickcheck.rs
@@ -6,6 +6,7 @@ use crate::{
     time_mod::Time,
     utc_offset::UtcOffset,
     util::days_in_year,
+    weekday::Weekday,
 };
 use quickcheck::{Arbitrary, Gen};
 use rand::Rng;
@@ -183,3 +184,28 @@ impl Arbitrary for OffsetDateTime {
         Box::new(shrunk_datetime.chain(shrunk_offset))
     }
 }
+
+impl Arbitrary for Weekday {
+    fn arbitrary<G>(g: &mut G) -> Self
+    where
+        G: Gen,
+    {
+        use Weekday::*;
+        match g.gen_range(0, max(1, min(7, g.size()))) {
+            0 => Monday,
+            1 => Tuesday,
+            2 => Wednesday,
+            3 => Thursday,
+            4 => Friday,
+            5 => Saturday,
+            _ => Sunday,
+        }
+    }
+
+    fn shrink(&self) -> Box<dyn Iterator<Item = Self>> {
+        match self {
+            Self::Monday => Box::new(std::iter::empty()),
+            _ => Box::new(std::iter::once(self.previous())),
+        }
+    }
+}
diff --git a/time-quickcheck-tests/tests/quickcheck.rs b/time-quickcheck-tests/tests/quickcheck.rs
@@ -12,6 +12,7 @@ use time::OffsetDateTime;
 use time::PrimitiveDateTime;
 use time::Time;
 use time::UtcOffset;
+use time::Weekday;
 
 /// Returns a statically seeded generator to ensure tests are deterministic
 fn make_generator(size: usize) -> StdGen<StdRng> {
@@ -280,3 +281,27 @@ fn arbitrary_offset_date_time_respects_generator_size() {
     test_generator_size!(OffsetDateTime, offset().as_seconds().abs(), 1000);
     test_generator_size!(OffsetDateTime, offset().as_seconds().abs(), 100_000);
 }
+
+quickcheck! {
+    fn weekday_supports_arbitrary(w: Weekday) -> bool {
+        w.iso_weekday_number() >= 1 && w.iso_weekday_number() <= 7
+    }
+
+    fn weekday_can_shrink(w: Weekday) -> bool {
+        match w {
+            Weekday::Monday => w.shrink().next() == None,
+            _ => w.shrink().next() == Some(w.previous())
+        }
+    }
+}
+
+#[test]
+fn arbitrary_weekday_respects_generator_size() {
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 1);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 2);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 3);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 4);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 5);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 6);
+    test_generator_size!(Weekday, iso_weekday_number() min=1, 7);
+}