Merge pull request #2746 from rivy/fix.factor

fix/factor ~ minor repairs to docs and tests

src/uu/factor/BENCHMARKING.md

@@ -44,7 +44,8 @@ on Daniel Lemire's [*Microbenchmarking calls for idealized conditions*][lemire],
 which I recommend reading if you want to add benchmarks to `factor`.
 
 1. Select a small, self-contained, deterministic component
-   `gcd` and `table::factor` are good example of such:
+   (`gcd` and `table::factor` are good examples):
+
    - no I/O or access to external data structures ;
    - no call into other components ;
    - behavior is deterministic: no RNG, no concurrency, ... ;
@@ -53,16 +54,19 @@ which I recommend reading if you want to add benchmarks to `factor`.
      maximizing the numbers of samples we can take in a given time.
 
 2. Benchmarks are immutable (once merged in `uutils`)
+
    Modifying a benchmark means previously-collected values cannot meaningfully
    be compared, silently giving nonsensical results.  If you must modify an
    existing benchmark, rename it.
 
 3. Test common cases
+
    We are interested in overall performance, rather than specific edge-cases;
    use **reproducibly-randomized inputs**, sampling from either all possible
    input values or some subset of interest.
 
 4. Use [`criterion`], `criterion::black_box`, ...
+
    `criterion` isn't perfect, but it is also much better than ad-hoc
    solutions in each benchmark.
 

src/uu/factor/src/numeric/gcd.rs

@@ -52,7 +52,7 @@ pub fn gcd(mut u: u64, mut v: u64) -> u64 {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use quickcheck::quickcheck;
+    use quickcheck::{quickcheck, TestResult};
 
     quickcheck! {
         fn euclidean(a: u64, b: u64) -> bool {
@@ -76,13 +76,12 @@ mod tests {
             gcd(0, a) == a
         }
 
-        fn divisor(a: u64, b: u64) -> () {
+        fn divisor(a: u64, b: u64) -> TestResult {
             // Test that gcd(a, b) divides a and b, unless a == b == 0
-            if a == 0 && b == 0 { return; }
+            if a == 0 && b == 0 { return TestResult::discard(); } // restrict test domain to !(a == b == 0)
 
             let g = gcd(a, b);
-            assert_eq!(a % g, 0);
+            TestResult::from_bool( g != 0 && a % g == 0 && b % g == 0 )
-            assert_eq!(b % g, 0);
         }
 
         fn commutative(a: u64, b: u64) -> bool {