Bug 1610626 - Fix wrench reftest mode incorrectly printing unexpected in some cases. r=Bert

The semantics of the inaccuracy reftest mode are that the overall
test succeeds as long as one of the multiple test images mismatches
the reference image.

However, the previous implementation would print an unexpected result
if any of the comparisons were equal (even though the overall test
result would be reported correctly).

This patch changes wrench so that it only reports an unexpected
failure for the overall test, not each individual reference.

Differential Revision: https://phabricator.services.mozilla.com/D60564

--HG--
extra : moz-landing-system : lando

gfx/wr/wrench/src/reftest.rs

@@ -149,21 +149,10 @@ impl Reftest {
         }
     }
 
-    /// Check the negative case (expecting inequality) and report details if same
+    /// Report details of the negative case
-    fn check_and_report_inequality_failure(
+    fn report_unexpected_equality(&self) {
-        &self,
-        comparison: ReftestImageComparison,
-    ) -> bool {
-        match comparison {
-            ReftestImageComparison::Equal => {
         println!("REFTEST TEST-UNEXPECTED-FAIL | {} | image comparison", self);
         println!("REFTEST TEST-END | {}", self);
-                false
-            }
-            ReftestImageComparison::NotEqual { .. } => {
-                true
-            }
-        }
     }
 }
 
@@ -704,7 +693,15 @@ impl<'a> ReftestHarness<'a> {
                 // Ensure that the final image *doesn't* match the reference
                 let test = images.pop().unwrap();
                 let comparison = test.compare(&reference);
-                t.check_and_report_inequality_failure(comparison)
+                match comparison {
+                    ReftestImageComparison::Equal => {
+                        t.report_unexpected_equality();
+                        false
+                    }
+                    ReftestImageComparison::NotEqual { .. } => {
+                        true
+                    }
+                }
             }
             ReftestOp::Accurate => {
                 // Ensure that *all* images match the reference
@@ -724,14 +721,18 @@ impl<'a> ReftestHarness<'a> {
             }
             ReftestOp::Inaccurate => {
                 // Ensure that at least one of the images doesn't match the reference
-                let mut found_mismatch = false;
+                let all_same = images.iter().all(|image| {
+                    match image.compare(&reference) {
+                        ReftestImageComparison::Equal => true,
+                        ReftestImageComparison::NotEqual { .. } => false,
+                    }
+                });
 
-                for test in images.drain(..) {
+                if all_same {
-                    let comparison = test.compare(&reference);
+                    t.report_unexpected_equality();
-                    found_mismatch |= t.check_and_report_inequality_failure(comparison);
                 }
 
-                found_mismatch
+                !all_same
             }
         }
     }