[Mock Canvas] paints...arc() is missing ability to test start and end arc angles.

Use case

The paints..arc() is missing the ability to test start and end arc angles. You can test total arc rect but cannot test where the arc begins and ends. Testing arc drawn path is crucial. As a workaround, golden tests can be used to capture the arc start and end path visually.

flutter/packages/flutter_test/lib/src/mock_canvas.dart

Lines 968 to 987 in 9e273d5

    
           @override 
        
           void arc({ 
        
             Rect? rect, 
        
             Color? color, 
        
             double? strokeWidth, 
        
             bool? hasMaskFilter, 
        
             PaintingStyle? style, 
        
             StrokeCap? strokeCap, 
        
           }) { 
        
             _predicates.add( 
        
               _ArcPaintPredicate( 
        
                 rect: rect, 
        
                 color: color, 
        
                 strokeWidth: strokeWidth, 
        
                 hasMaskFilter: hasMaskFilter, 
        
                 style: style, 
        
                 strokeCap: strokeCap, 
        
               ), 
        
             ); 
        
           }

See the arc API for angles parameters :

https://api.flutter.dev/flutter/dart-ui/Canvas/drawArc.html

Proposal

Add ability to test arc start and end angles in paints..arc()

Any time we can trade image diff testing for regular unit testing it's a big win in terms of test performance and reducing time spent fixing irrelevant test failures, so I'm definitely on board with this 👍 . I'm not an expert on what it would take to make this change but hopefully someone else has context.

labelling this as a valid proposal

Add missing properties to _ArcPaintPredicate. (#162572)

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

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[Mock Canvas] `paints...arc()` is missing ability to test start and end arc angles. #162317

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	@override
	void arc({
	Rect? rect,
	Color? color,
	double? strokeWidth,
	bool? hasMaskFilter,
	PaintingStyle? style,
	StrokeCap? strokeCap,
	}) {
	_predicates.add(
	_ArcPaintPredicate(
	rect: rect,
	color: color,
	strokeWidth: strokeWidth,
	hasMaskFilter: hasMaskFilter,
	style: style,
	strokeCap: strokeCap,
	),
	);
	}

[Mock Canvas] paints...arc() is missing ability to test start and end arc angles. #162317

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justinmc commented on Jan 28, 2025

maheshj01 commented on Jan 29, 2025

github-actions commented on Mar 4, 2025

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[Mock Canvas] `paints...arc()` is missing ability to test start and end arc angles. #162317