[ios, macos] Snapshot-test runtime styling in snapshots

platform/darwin/test/MGLMapSnapshotterTests.m

@@ -1,9 +1,58 @@
 #import <Mapbox/Mapbox.h>
 #import <XCTest/XCTest.h>
 
+MGLImage *MGLNormalizedImage(MGLImage *sourceImage) {
+#if TARGET_OS_IPHONE
+    CGSize scaledSize = CGSizeMake(sourceImage.size.width * sourceImage.scale, sourceImage.size.height * sourceImage.scale);
+    UIGraphicsBeginImageContextWithOptions(scaledSize, NO, UIScreen.mainScreen.scale);
+    [sourceImage drawInRect:(CGRect){ .origin = CGPointZero, .size = scaledSize }];
+    UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
+    UIGraphicsEndImageContext();
+    return normalizedImage;
+#else
+    return [NSImage imageWithSize:sourceImage.size flipped:NO drawingHandler:^BOOL(NSRect dstRect) {
+        [sourceImage drawInRect:dstRect];
+        return YES;
+    }];
+#endif
+}
+
+BOOL MGLEqualImages(MGLImage *leftImage, MGLImage *rightImage) {
+#if TARGET_OS_IPHONE
+    NSData *leftData = UIImagePNGRepresentation(MGLNormalizedImage(leftImage));
+    NSData *rightData = UIImagePNGRepresentation(MGLNormalizedImage(rightImage));
+    return [leftData isEqualToData:rightData];
+#else
+    CGImageRef leftCGImage = [MGLNormalizedImage(leftImage) CGImageForProposedRect:nil context:nil hints:nil];
+    NSBitmapImageRep *leftImageRep = [[NSBitmapImageRep alloc] initWithCGImage:leftCGImage];
+    NSData *leftData = [leftImageRep representationUsingType:NSPNGFileType properties:@{}];
+    
+    CGImageRef rightCGImage = [MGLNormalizedImage(rightImage) CGImageForProposedRect:nil context:nil hints:nil];
+    NSBitmapImageRep *rightImageRep = [[NSBitmapImageRep alloc] initWithCGImage:rightCGImage];
+    NSData *rightData = [rightImageRep representationUsingType:NSPNGFileType properties:@{}];
+    
+    return [leftData isEqualToData:rightData];
+#endif
+}
+
+MGLImage *MGLImageFromCurrentContext() {
+#if TARGET_OS_IPHONE
+    return UIGraphicsGetImageFromCurrentImageContext();
+#else
+    CGContextRef context = NSGraphicsContext.currentContext.CGContext;
+    CGImageRef cgImage = CGBitmapContextCreateImage(context);
+    CGFloat scale = NSScreen.mainScreen.backingScaleFactor;
+    NSSize imageSize = NSMakeSize(CGImageGetWidth(cgImage) / scale, CGImageGetHeight(cgImage) / scale);
+    NSImage *image = [[NSImage alloc] initWithCGImage:cgImage size:imageSize];
+    CGImageRelease(cgImage);
+    return image;
+#endif
+}
+
 @interface MGLMapSnapshotterTests : XCTestCase <MGLMapSnapshotterDelegate>
 
 @property (nonatomic) XCTestExpectation *styleLoadingExpectation;
+@property (nonatomic, copy, nullable) void (^runtimeStylingActions)(MGLStyle *style);
 
 @end
 
@@ -22,6 +71,7 @@
 - (void)tearDown {
     [MGLAccountManager setAccessToken:nil];
     self.styleLoadingExpectation = nil;
+    self.runtimeStylingActions = nil;
     [super tearDown];
 }
 
@@ -39,9 +89,6 @@
     NSImage *blankImage = [NSImage imageWithSize:NSMakeSize(500, 500) flipped:NO drawingHandler:^BOOL(NSRect dstRect) {
         return YES;
     }];
-    CGImageRef blankCGImage = [blankImage CGImageForProposedRect:nil context:nil hints:nil];
-    NSBitmapImageRep *blankImageRep = [[NSBitmapImageRep alloc] initWithCGImage:blankCGImage];
-    NSData *blankImageData = [blankImageRep representationUsingType:NSPNGFileType properties:@{}];
 #endif
     
     NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
@@ -55,15 +102,8 @@
         XCTAssertNotNil(snapshotOverlay);
         if (snapshotOverlay) {
             XCTAssertNotEqual(snapshotOverlay.context, NULL);
-#if TARGET_OS_IPHONE
-            UIImage *imageFromContext = UIGraphicsGetImageFromCurrentImageContext();
-            XCTAssertEqualObjects(UIImagePNGRepresentation(blankImage), UIImagePNGRepresentation(imageFromContext), @"Base map in snapshot should be blank.");
-#else
-            CGImageRef imageFromContext = CGBitmapContextCreateImage(snapshotOverlay.context);
-            NSBitmapImageRep *imageRep = [[NSBitmapImageRep alloc] initWithCGImage:imageFromContext];
-            NSData *imageData = [imageRep representationUsingType:NSPNGFileType properties:@{}];
-            XCTAssertEqualObjects(blankImageData, imageData, @"Base map in snapshot should be blank.");
-#endif
+            MGLImage *imageFromContext = MGLImageFromCurrentContext();
+            XCTAssertTrue(MGLEqualImages(blankImage, imageFromContext), @"Base map in snapshot should be blank.");
         }
         [overlayExpectation fulfill];
     } completionHandler:^(MGLMapSnapshot * _Nullable snapshot, NSError * _Nullable error) {
@@ -101,11 +141,71 @@
     [self waitForExpectations:@[self.styleLoadingExpectation, completionExpectation] timeout:2 enforceOrder:YES];
 }
 
+- (void)testRuntimeStyling {
+    [self testRuntimeStylingActions:^(MGLStyle *style) {
+        MGLBackgroundStyleLayer *backgroundLayer = [[MGLBackgroundStyleLayer alloc] initWithIdentifier:@"background"];
+        backgroundLayer.backgroundColor = [NSExpression expressionForConstantValue:[MGLColor orangeColor]];
+        [style addLayer:backgroundLayer];
+    } expectedImageName:@"Fixtures/MGLMapSnapshotterTests/background"];
+}
+
+/**
+ Tests that applying the given runtime styling actions on a blank style results in a snapshot image that matches the image with the given name in the asset catalog.
+ 
+ @param actions Runtime styling actions to apply to the blank style.
+ @param expectedImageName Name of the test fixture image in Media.xcassets.
+ */
+- (void)testRuntimeStylingActions:(void (^)(MGLStyle *style))actions expectedImageName:(NSString *)expectedImageName {
+    self.styleLoadingExpectation = [self expectationWithDescription:@"Style should finish loading."];
+    XCTestExpectation *overlayExpectation = [self expectationWithDescription:@"Overlay handler should get called."];
+    XCTestExpectation *completionExpectation = [self expectationWithDescription:@"Completion handler should get called."];
+    
+#if TARGET_OS_IPHONE
+    UIImage *expectedImage = [UIImage imageNamed:expectedImageName inBundle:[NSBundle bundleForClass:[self class]] compatibleWithTraitCollection:nil];
+#else
+    NSImage *expectedImage = [[NSBundle bundleForClass:[self class]] imageForResource:expectedImageName];
+#endif
+    XCTAssertNotNil(expectedImage, @"Image fixture “%@” missing from Media.xcassets.", expectedImageName);
+    
+    NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
+    MGLMapCamera *camera = [MGLMapCamera camera];
+    MGLMapSnapshotOptions *options = [[MGLMapSnapshotOptions alloc] initWithStyleURL:styleURL camera:camera size:CGSizeMake(500, 500)];
+    
+    MGLMapSnapshotter *snapshotter = [[MGLMapSnapshotter alloc] initWithOptions:options];
+    snapshotter.delegate = self;
+    self.runtimeStylingActions = actions;
+    
+    [snapshotter startWithOverlayHandler:^(MGLMapSnapshotOverlay * _Nonnull snapshotOverlay) {
+        XCTAssertNotNil(snapshotOverlay);
+        if (snapshotOverlay) {
+            XCTAssertNotEqual(snapshotOverlay.context, NULL);
+            MGLImage *actualImage = MGLImageFromCurrentContext();
+            XCTAssertTrue(MGLEqualImages(expectedImage, actualImage), @"Bare snapshot before ornamentation differs from expected image.");
+        }
+        [overlayExpectation fulfill];
+    } completionHandler:^(MGLMapSnapshot * _Nullable snapshot, NSError * _Nullable error) {
+        XCTAssertNil(error);
+        XCTAssertNotNil(snapshot);
+        if (snapshot) {
+            XCTAssertEqual(snapshot.image.size.width, 500);
+            XCTAssertEqual(snapshot.image.size.height, 500);
+        }
+        [completionExpectation fulfill];
+    }];
+    [self waitForExpectations:@[self.styleLoadingExpectation, overlayExpectation, completionExpectation] timeout:2 enforceOrder:YES];
+    self.runtimeStylingActions = nil;
+}
+
 #pragma mark MGLMapSnapshotterDelegate methods
 
 - (void)mapSnapshotter:(MGLMapSnapshotter *)snapshotter didFinishLoadingStyle:(MGLStyle *)style {
     XCTAssertNotNil(snapshotter);
     XCTAssertNotNil(style);
+    
+    if (self.runtimeStylingActions) {
+        self.runtimeStylingActions(style);
+    }
+    
     [self.styleLoadingExpectation fulfill];
 }
 

platform/darwin/test/Media.xcassets/Fixtures/Contents.json

@@ -0,0 +1,9 @@
+{
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  },
+  "properties" : {
+    "provides-namespace" : true
+  }
+}

platform/darwin/test/Media.xcassets/Fixtures/MGLMapSnapshotterTests/Contents.json

@@ -0,0 +1,9 @@
+{
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  },
+  "properties" : {
+    "provides-namespace" : true
+  }
+}

platform/darwin/test/Media.xcassets/Fixtures/MGLMapSnapshotterTests/background.imageset/Contents.json

@@ -0,0 +1,21 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "background.png",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}