Add tests for cis function

Author: rayhem

src/lib.rs

@@ -1609,6 +1609,15 @@ mod test {
         use super::*;
         use num_traits::{Float, Pow};
 
+        #[test]
+        fn test_cis() {
+            assert!(close(Complex::cis(0.0 * f64::consts::PI), _1_0i));
+            assert!(close(Complex::cis(0.5 * f64::consts::PI), _0_1i));
+            assert!(close(Complex::cis(1.0 * f64::consts::PI), -_1_0i));
+            assert!(close(Complex::cis(1.5 * f64::consts::PI), -_0_1i));
+            assert!(close(Complex::cis(2.0 * f64::consts::PI), _1_0i));
+        }
+
         #[test]
         #[cfg_attr(target_arch = "x86", ignore)]
         // FIXME #7158: (maybe?) currently failing on x86.