Add more context to polycool unit test failure messages (#595)

Author: wmedrano

polycool/src/arbitrary.rs

@@ -164,7 +164,12 @@ mod tests {
         arbtest::arbtest(|u| {
             let r = float_in_unit_interval(u)?;
             let p: Poly<6> = poly_with_planted_root(u, r, 1e-6)?;
-            assert!(p.eval(r).abs() <= 1e-12 * p.max_abs_coefficient().max(1.0));
+            let threshold = 1e-12 * p.max_abs_coefficient().max(1.0);
+            let y = p.eval(r);
+            assert!(
+                y.abs() <= threshold,
+                "poly {p:?} had planted root {r} evaluate to {y:?}, but expected |y| <= {threshold:?}"
+            );
             Ok(())
         });
     }

polycool/src/poly.rs

@@ -452,16 +452,28 @@ mod tests {
             }
             let roots = poly.roots_between(-2.0, 2.0, 1e-13);
 
-            assert!(roots.iter().all(|r| r.is_finite()));
+            assert!(
+                roots.iter().all(|r| r.is_finite()),
+                "found non-finite roots: {roots:?}"
+            );
 
             // Check that the roots are sorted.
-            assert!(roots.is_sorted());
-            assert!(roots.iter().all(|r| (-2.0..=2.0).contains(r)));
+            assert!(
+                roots.is_sorted(),
+                "roots are not sorted: {roots:?}"
+            );
+            assert!(
+                roots.iter().all(|r| (-2.0..=2.0).contains(r)),
+                "found roots out of range [-2.0, 2.0]: {roots:?}"
+            );
 
             // We can't expect great accuracy for huge coefficients, because the
             // evaluations during Newton iteration are subject to error.
             let error = poly.max_abs_coefficient().max(1.0) * 1e-12;
-            assert!(roots.iter().any(|r| (r - planted_root).abs() <= error));
+            assert!(
+                roots.iter().any(|r| (r - planted_root).abs() <= error),
+                "could not find something close to planted_root {planted_root} in found {roots:?} with allowed error {error} for poly {poly:?}"
+            );
             Ok(())
         })
         .budget_ms(5_000);

polycool/src/quadratic.rs

@@ -125,7 +125,10 @@ mod tests {
                 let r_magnitude = r.abs().max(1.0);
                 let threshold = r_magnitude * 1e-14 * r_magnitude * magnitude;
                 if y.is_finite() && threshold.is_finite() {
-                    assert!(y.abs() <= threshold);
+                    assert!(
+                        y.abs() <= threshold,
+                        "quadratic {q:?} had root {r} evaluate to {y:?}, but expected |y| <= {threshold:?}"
+                    );
                 }
             }
             Ok(())