Fix the test case compile warning of `SDWebImageTestDiskCache`

Tests/Tests/SDWebImageTestCache.m

@@ -9,6 +9,9 @@
 
 #import "SDWebImageTestCache.h"
 #import <SDWebImage/SDImageCacheConfig.h>
+#import "SDFileAttributeHelper.h"
+
+static NSString * const SDWebImageTestDiskCacheExtendedAttributeName = @"com.hackemist.SDWebImageTestDiskCache";
 
 @implementation SDWebImageTestMemoryCache
 
@@ -104,4 +107,18 @@
     return size;
 }
 
+- (nullable NSData *)extendedDataForKey:(nonnull NSString *)key {
+    NSString *cachePathForKey = [self cachePathForKey:key];
+    return [SDFileAttributeHelper extendedAttribute:SDWebImageTestDiskCacheExtendedAttributeName atPath:cachePathForKey traverseLink:NO error:nil];
+}
+
+- (void)setExtendedData:(nullable NSData *)extendedData forKey:(nonnull NSString *)key {
+    NSString *cachePathForKey = [self cachePathForKey:key];
+    if (!extendedData) {
+        [SDFileAttributeHelper removeExtendedAttribute:SDWebImageTestDiskCacheExtendedAttributeName atPath:cachePathForKey traverseLink:NO error:nil];
+    } else {
+        [SDFileAttributeHelper setExtendedAttribute:SDWebImageTestDiskCacheExtendedAttributeName value:extendedData atPath:cachePathForKey traverseLink:NO overwrite:YES error:nil];
+    }
+}
+
 @end