BadNote/test/pen_config_test.dart

// test/pen_config_test.dart
//
// Unit tests for PenConfig (toJson/fromJson round-trip) and
// applyPressureCurve. No widgets, no SharedPreferences, no Flutter framework.

import 'package:flutter_test/flutter_test.dart';
import 'package:badnote/editor/engine/stroke_geometry.dart'
    show kDefaultPenThinning;
import 'package:badnote/editor/input/pen_config.dart';

void main() {
  group('applyPressureCurve', () {
    test('gamma=1 is identity', () {
      expect(applyPressureCurve(0.5, 1.0), closeTo(0.5, 1e-9));
      expect(applyPressureCurve(0.0, 1.0), closeTo(0.0, 1e-9));
      expect(applyPressureCurve(1.0, 1.0), closeTo(1.0, 1e-9));
    });

    test('applyPressureCurve(0.5, 2.0) == 0.25', () {
      expect(applyPressureCurve(0.5, 2.0), closeTo(0.25, 1e-9));
    });

    test('clamps input below 0', () {
      expect(applyPressureCurve(-0.5, 1.0), closeTo(0.0, 1e-9));
    });

    test('clamps input above 1', () {
      expect(applyPressureCurve(1.5, 1.0), closeTo(1.0, 1e-9));
    });
  });

  group('PenConfig toJson / fromJson round-trip', () {
    test('default config survives round-trip', () {
      const original = PenConfig();
      final restored = PenConfig.fromJson(original.toJson());
      expect(restored, equals(original));
    });

    test('custom config survives round-trip', () {
      const original = PenConfig(
        sideButton: PenButtonAction.undo,
        eraserEnd: PenButtonAction.pan,
        pressureGamma: 1.5,
        palmRejectionMs: 200.0,
        fingerDrawing: true,
        penWidth: 0.008,
        highlighterWidth: 0.03,
        pressureSensitivity: 0.42,
      );
      final restored = PenConfig.fromJson(original.toJson());
      expect(restored, equals(original));
      expect(restored.pressureSensitivity, 0.42);
    });

    test('fromJson falls back to defaults for missing keys', () {
      final restored = PenConfig.fromJson({});
      expect(restored.sideButton, PenButtonAction.eraser);
      expect(restored.eraserEnd, PenButtonAction.eraser);
      expect(restored.pressureGamma, 1.0);
      expect(restored.palmRejectionMs, 150.0);
      expect(restored.fingerDrawing, false);
      expect(restored.penWidth, 0.004);
      expect(restored.highlighterWidth, 0.02);
      // Missing pressureSensitivity defaults to the shared thinning constant,
      // preserving the pre-existing stroke feel + export golden (plan M4).
      expect(restored.pressureSensitivity, kDefaultPenThinning);
    });

    test('fromJson falls back to defaults for unknown enum names', () {
      final restored = PenConfig.fromJson({
        'sideButton': 'unknownAction',
        'eraserEnd': 'anotherUnknown',
      });
      expect(restored.sideButton, PenButtonAction.eraser);
      expect(restored.eraserEnd, PenButtonAction.eraser);
    });
  });

  group('PenConfig copyWith', () {
    test('copyWith preserves unchanged fields', () {
      const original = PenConfig(pressureGamma: 2.0);
      final copy = original.copyWith(fingerDrawing: true);
      expect(copy.pressureGamma, 2.0);
      expect(copy.fingerDrawing, true);
    });
  });
}