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Add imprecise comparison variants to iOSSnapshotTestCase extension
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This adds variants of the `SnapshotVerify*(...)` methods that allow for imprecise comparisons, i.e. using the `perPixelTolerance` and `overallTolerance` parameters.

 ## Why is this necessary?

Adding tolerances has been a highly requested feature (see #63) to work around some simulator changes introduced in iOS 13. Historically the simulator has supported CPU-based rendering, giving us very stable image representations of views that we can compare pixel-by-pixel. Unfortunately, with iOS 13, Apple changed the simulator to use exclusively GPU-based rendering, which means that the resulting snapshots may differ slightly across machines (see uber/ios-snapshot-test-case#109).

The negative effects of this were mitigated in iOSSnapshotTestCase by adding two tolerances: a **per-pixel tolerance** that controls how close in color two pixels need to be to count as unchanged and an **overall tolerance** that controls what portion of pixels between two images need to be the same (based on the per-pixel calculation) for the images to be considered unchanged. Setting these tolerances to non-zero values enables engineers to record tests on one machine and run them on another without worrying about the tests failing due to differences in GPU rendering.
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NickEntin committed Aug 15, 2023
1 parent cf1f342 commit 4168221
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Showing 15 changed files with 362 additions and 25 deletions.
4 changes: 4 additions & 0 deletions Example/AccessibilitySnapshot.xcodeproj/project.pbxproj
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3D3F2E142263E6B900F7608E /* InvertColorsViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3D3F2E132263E6B900F7608E /* InvertColorsViewController.swift */; };
3D3F2E162263E94D00F7608E /* InvertColorsTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3D3F2E152263E94D00F7608E /* InvertColorsTests.swift */; };
3D4674682116A3F100278B57 /* ViewAccessibilityPropertiesViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3D4674672116A3F100278B57 /* ViewAccessibilityPropertiesViewController.swift */; };
3D9334942A8B2E520078A142 /* ImpreciseObjectiveCTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 3D9334932A8B2E520078A142 /* ImpreciseObjectiveCTests.m */; };
3D9894F9213509C8006C16F6 /* DescriptionEdgeCasesViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3D9894F8213509C8006C16F6 /* DescriptionEdgeCasesViewController.swift */; };
3DA12A3222405B9E00EB3C33 /* DataTableViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3DA12A3122405B9E00EB3C33 /* DataTableViewController.swift */; };
3DBAC28722406EBB00EF4D0A /* AccessibilityContainersTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3DBAC28622406EBB00EF4D0A /* AccessibilityContainersTests.swift */; };
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3D4674672116A3F100278B57 /* ViewAccessibilityPropertiesViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ViewAccessibilityPropertiesViewController.swift; sourceTree = "<group>"; };
3D881956246E03C00061DA6A /* UnitTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = UnitTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
3D88195A246E03C00061DA6A /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
3D9334932A8B2E520078A142 /* ImpreciseObjectiveCTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = ImpreciseObjectiveCTests.m; sourceTree = "<group>"; };
3D9894F8213509C8006C16F6 /* DescriptionEdgeCasesViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DescriptionEdgeCasesViewController.swift; sourceTree = "<group>"; };
3DA12A3122405B9E00EB3C33 /* DataTableViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DataTableViewController.swift; sourceTree = "<group>"; };
3DBAC28622406EBB00EF4D0A /* AccessibilityContainersTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccessibilityContainersTests.swift; sourceTree = "<group>"; };
Expand Down Expand Up @@ -294,6 +296,7 @@
isa = PBXGroup;
children = (
3D13DB512221124000066519 /* ObjectiveCTests.m */,
3D9334932A8B2E520078A142 /* ImpreciseObjectiveCTests.m */,
3DBAC28622406EBB00EF4D0A /* AccessibilityContainersTests.swift */,
607FACEB1AFB9204008FA782 /* AccessibilityPropertiesTests.swift */,
3D39BFAF2239BC42009C3EF4 /* ActivationPointTests.swift */,
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3D220A2B252AF72900359C1E /* AccessibleContainerView.swift in Sources */,
1635CE4E251EAC6700907101 /* SnapshotTestingTests.swift in Sources */,
3DBEAA5D2223C0CE00FAE61D /* SwitchControlsTests.swift in Sources */,
3D9334942A8B2E520078A142 /* ImpreciseObjectiveCTests.m in Sources */,
3DF46500220D5FB00048D446 /* ElementSelectionTests.swift in Sources */,
3DBAC28722406EBB00EF4D0A /* AccessibilityContainersTests.swift in Sources */,
3DC488392212B40C006D1E15 /* ModalTests.swift in Sources */,
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92 changes: 92 additions & 0 deletions Example/SnapshotTests/ImpreciseObjectiveCTests.m
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//
// Copyright 2023 Block Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

@import AccessibilitySnapshot;
@import FBSnapshotTestCase;
@import XCTest;


@interface ImpreciseObjectiveCTests : FBSnapshotTestCase

@end


@implementation ImpreciseObjectiveCTests

- (void)setUp;
{
[super setUp];

self.fileNameOptions = FBSnapshotTestCaseFileNameIncludeOptionOS | FBSnapshotTestCaseFileNameIncludeOptionScreenSize | FBSnapshotTestCaseFileNameIncludeOptionScreenScale;
}

- (void)testSimpleView;
{
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 50)];

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(25, 10, 150, 30)];
label.text = @"Objective-C Snapshot";
label.textColor = [UIColor redColor];
label.font = [UIFont systemFontOfSize:12];
label.textAlignment = NSTextAlignmentCenter;
[view addSubview:label];

SnapshotImpreciseVerifyAccessibility(view, nil, 0, 0);
}

- (void)testSimpleViewWithIdentifier;
{
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 50)];

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(25, 10, 150, 30)];
label.text = @"Objective-C Snapshot";
label.textColor = [UIColor redColor];
label.font = [UIFont systemFontOfSize:12];
label.textAlignment = NSTextAlignmentCenter;
[view addSubview:label];

SnapshotImpreciseVerifyAccessibility(view, @"identifier", 0, 0);
}

- (void)testSimpleViewWithActivationPointAlways;
{
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 50)];

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(25, 10, 150, 30)];
label.text = @"Objective-C Snapshot";
label.textColor = [UIColor redColor];
label.font = [UIFont systemFontOfSize:12];
label.textAlignment = NSTextAlignmentCenter;
[view addSubview:label];

SnapshotImpreciseVerifyAccessibilityWithOptions(view, nil, YES, YES, 0, 0);
}

- (void)testViewWithInvertedColors;
{
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[view setBackgroundColor:[UIColor redColor]];

UIView *subview = [[UIView alloc] initWithFrame:CGRectMake(25, 25, 50, 50)];
[subview setBackgroundColor:[UIColor greenColor]];

[subview setAccessibilityIgnoresInvertColors:YES];
[view addSubview:subview];

SnapshotImpreciseVerifyWithInvertedColors(view, nil, 0, 0);
}

@end
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Original file line number Diff line number Diff line change
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//
// Copyright 2019 Square Inc.
// Copyright 2023 Block Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
Expand All @@ -18,11 +18,11 @@
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:);\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *);\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyAccessibility = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"");\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"", 0, 0);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
Expand All @@ -34,11 +34,11 @@
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:showActivationPoints:useMonochromeSnapshot:);\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:showActivationPoints:useMonochromeSnapshot:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, BOOL, BOOL);\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, BOOL, BOOL, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyAccessibility = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"", showActivationPoints__, useMonochromeSnapshot__);\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"", showActivationPoints__, useMonochromeSnapshot__, 0, 0);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
Expand All @@ -50,11 +50,11 @@
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyWithInvertedColors:identifier:);\
SEL selector = @selector(snapshotVerifyWithInvertedColors:identifier:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *);\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyWithInvertedColors = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyWithInvertedColors(self, selector, view__, identifier__ ?: @"");\
NSString *errorDescription = snapshotVerifyWithInvertedColors(self, selector, view__, identifier__ ?: @"", 0, 0);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
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//
// Copyright 2023 Block Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#define SnapshotImpreciseVerifyAccessibility(view__, identifier__, perPixelTolerance__, overallTolerance__)\
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyAccessibility = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"", perPixelTolerance__, overallTolerance__);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
XCTFail("%@", errorDescription);\
}\
}

#define SnapshotImpreciseVerifyAccessibilityWithOptions(view__, identifier__, showActivationPoints__, useMonochromeSnapshot__, perPixelTolerance__, overallTolerance__)\
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyAccessibility:identifier:showActivationPoints:useMonochromeSnapshot:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, BOOL, BOOL, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyAccessibility = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyAccessibility(self, selector, view__, identifier__ ?: @"", showActivationPoints__, useMonochromeSnapshot__, perPixelTolerance__, overallTolerance__);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
XCTFail("%@", errorDescription);\
}\
}

#define SnapshotImpreciseVerifyWithInvertedColors(view__, identifier__, perPixelTolerance__, overallTolerance__)\
{\
_Pragma("clang diagnostic push")\
_Pragma("clang diagnostic ignored \"-Wundeclared-selector\"")\
SEL selector = @selector(snapshotVerifyWithInvertedColors:identifier:perPixelTolerance:overallTolerance:);\
_Pragma("clang diagnostic pop")\
typedef NSString * (*SnapshotMethod)(id, SEL, UIView *, NSString *, CGFloat, CGFloat);\
SnapshotMethod snapshotVerifyWithInvertedColors = (SnapshotMethod)[self methodForSelector:selector];\
NSString *errorDescription = snapshotVerifyWithInvertedColors(self, selector, view__, identifier__ ?: @"", perPixelTolerance__, overallTolerance__);\
if (errorDescription == nil) {\
XCTAssertTrue(YES);\
} else {\
XCTFail("%@", errorDescription);\
}\
}
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
//
// Copyright 2019 Square Inc.
// Copyright 2023 Block Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
Expand Down
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