From 172a3930f79f3e0a8c7ccc4987e18bc223643eaf Mon Sep 17 00:00:00 2001
From: Chris Yang <ychris@google.com>
Date: Fri, 30 Oct 2020 13:05:34 -0700
Subject: [PATCH] Report image diff status for iOS scenario golden tests
 (#22230)

---
 .../ios/Scenarios/ScenariosUITests/GoldenImage.m    | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/testing/scenario_app/ios/Scenarios/ScenariosUITests/GoldenImage.m b/testing/scenario_app/ios/Scenarios/ScenariosUITests/GoldenImage.m
index 909cac11c..cc622d7df 100644
--- a/testing/scenario_app/ios/Scenarios/ScenariosUITests/GoldenImage.m
+++ b/testing/scenario_app/ios/Scenarios/ScenariosUITests/GoldenImage.m
@@ -5,6 +5,7 @@
 #import "GoldenImage.h"
 
 #import <XCTest/XCTest.h>
+#import <os/log.h>
 #include <sys/sysctl.h>
 
 static const double kRmseThreshold = 0.5;
@@ -29,6 +30,7 @@ static const double kRmseThreshold = 0.5;
 
 - (BOOL)compareGoldenToImage:(UIImage*)image {
   if (!self.image || !image) {
+    os_log_error(OS_LOG_DEFAULT, "GOLDEN DIFF FAILED: image does not exists.");
     return NO;
   }
   CGImageRef imageRefA = [self.image CGImage];
@@ -40,6 +42,7 @@ static const double kRmseThreshold = 0.5;
   NSUInteger heightB = CGImageGetHeight(imageRefB);
 
   if (widthA != widthB || heightA != heightB) {
+    os_log_error(OS_LOG_DEFAULT, "GOLDEN DIFF FAILED: images sizes do not match.");
     return NO;
   }
   NSUInteger bytesPerPixel = 4;
@@ -48,6 +51,7 @@ static const double kRmseThreshold = 0.5;
   NSMutableData* rawB = [NSMutableData dataWithLength:size];
 
   if (!rawA || !rawB) {
+    os_log_error(OS_LOG_DEFAULT, "GOLDEN DIFF FAILED: image data length do not match.");
     return NO;
   }
 
@@ -87,7 +91,14 @@ static const double kRmseThreshold = 0.5;
     }
   }
   double rmse = sqrt(sum / size);
-  return rmse <= kRmseThreshold;
+  if (rmse > kRmseThreshold) {
+    os_log_error(
+        OS_LOG_DEFAULT,
+        "GOLDEN DIFF FAILED: image diff greater than threshold. Current diff: %@, threshold: %@",
+        @(rmse), @(kRmseThreshold));
+    return NO;
+  }
+  return YES;
 }
 
 NS_INLINE NSString* _platformName() {
-- 
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