Fix the unit test `test31ThatMultipleRequestForSameURLFailedCallback`

Tests/Tests/SDImageCoderTests.m

@@ -541,6 +541,8 @@
 #if SD_UIKIT
     UIImageOrientation orientation = image.imageOrientation;
     expect(orientation).equal(UIImageOrientationUp);
+#else
+    expect(image.sd_imageFormat).equal(SDImageFormatJPEG);
 #endif
     
     // Manual test again for Apple's API

Tests/Tests/SDWebImageDownloaderTests.m

@@ -825,14 +825,17 @@
     [self waitForExpectations:expectations timeout:kAsyncTestTimeout * 2];
 }
 
-
 - (void)test31ThatMultipleRequestForSameURLFailedCallback {
     // See #3493, silly bug
-    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"]; // Always fail url
-    NSMutableArray<XCTestExpectation *> *expectations = [NSMutableArray arrayWithCapacity:100];
+    // Create tmp file with empty contents
+    NSURL *dir = [[NSURL fileURLWithPath:NSTemporaryDirectory()] URLByAppendingPathComponent:NSStringFromSelector(_cmd) isDirectory: true];
+    [NSFileManager.defaultManager createDirectoryAtURL:dir withIntermediateDirectories:YES attributes:nil error:nil];
+    NSURL *url = [dir URLByAppendingPathComponent:@"file" isDirectory:NO];
+    [[NSData data] writeToURL:url atomically:YES]; // Always fail url (but valid)
+    NSMutableArray<XCTestExpectation *> *expectations = [NSMutableArray arrayWithCapacity:10];
     __block void (^recursiveBlock)(int);
     void (^mainBlock)(int) = ^(int i) {
-        if (i > 200) return;
+        if (i > 10) return;
         NSString *desc = [NSString stringWithFormat:@"Failed url with index %d should callback error", i];
         XCTestExpectation *expectation = [self expectationWithDescription:desc];
         [expectations addObject:expectation];
@@ -853,7 +856,6 @@
     [self waitForExpectations:expectations timeout:kAsyncTestTimeout * 2];
 }
 
-
 #pragma mark - SDWebImageLoader
 - (void)testCustomImageLoaderWorks {
     XCTestExpectation *expectation = [self expectationWithDescription:@"Custom image not works"];