packages/flutter/test/services/text_boundary_test.dart - mirrors/flutter - Git at Google

 // Copyright 2014 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';


 class _ConsistentTextRangeImplementationMatcher extends Matcher {
   _ConsistentTextRangeImplementationMatcher(int length)
     : range = TextRange(start: -1, end: length + 1),
       assert(length >= 0);

   final TextRange range;
   @override
   Description describe(Description description) {
     return description.add('The implementation of TextBoundary.getTextBoundaryAt is consistent with its other methods.');
   }

   @override
   Description describeMismatch(dynamic item, Description mismatchDescription, Map<dynamic, dynamic> matchState, bool verbose) {
     final TextBoundary boundary = matchState['textBoundary'] as TextBoundary;
     final int position = matchState['position'] as int;
     final int leading = boundary.getLeadingTextBoundaryAt(position) ?? -1;
     final int trailing = boundary.getTrailingTextBoundaryAt(position) ?? -1;

     return mismatchDescription.add(
       'at position $position, expected ${TextRange(start: leading, end: trailing)} but got ${boundary.getTextBoundaryAt(position)}',
     );
   }

   @override
   bool matches(dynamic item, Map<dynamic, dynamic> matchState) {
     for (int i = range.start; i <= range.end; i++) {
       final int? leading = (item as TextBoundary).getLeadingTextBoundaryAt(i);
       final int? trailing = item.getTrailingTextBoundaryAt(i);
       final TextRange boundary = item.getTextBoundaryAt(i);
       final bool consistent = boundary.start == (leading ?? -1) && boundary.end == (trailing ?? -1);
       if (!consistent) {
         matchState['textBoundary'] = item;
         matchState['position'] = i;
         return false;
       }
     }
     return true;
   }
 }

 Matcher _hasConsistentTextRangeImplementationWithinRange(int length) => _ConsistentTextRangeImplementationMatcher(length);

 void main() {
   test('Character boundary works', () {
     const CharacterBoundary boundary = CharacterBoundary('abc');
     expect(boundary, _hasConsistentTextRangeImplementationWithinRange(3));

     expect(boundary.getLeadingTextBoundaryAt(-1), null);
     expect(boundary.getTrailingTextBoundaryAt(-1), 0);

     expect(boundary.getLeadingTextBoundaryAt(0), 0);
     expect(boundary.getTrailingTextBoundaryAt(0), 1);

     expect(boundary.getLeadingTextBoundaryAt(1), 1);
     expect(boundary.getTrailingTextBoundaryAt(1), 2);

     expect(boundary.getLeadingTextBoundaryAt(2), 2);
     expect(boundary.getTrailingTextBoundaryAt(2), 3);

     expect(boundary.getLeadingTextBoundaryAt(3), 3);
     expect(boundary.getTrailingTextBoundaryAt(3), null);

     expect(boundary.getLeadingTextBoundaryAt(4), 3);
     expect(boundary.getTrailingTextBoundaryAt(4), null);
   });

   test('Character boundary works with grapheme', () {
     const String text = 'a❄︎c';
     const CharacterBoundary boundary = CharacterBoundary(text);
     expect(boundary, _hasConsistentTextRangeImplementationWithinRange(text.length));

     expect(boundary.getLeadingTextBoundaryAt(-1), null);
     expect(boundary.getTrailingTextBoundaryAt(-1), 0);

     expect(boundary.getLeadingTextBoundaryAt(0), 0);
     expect(boundary.getTrailingTextBoundaryAt(0), 1);

     // The `❄` takes two character length.
     expect(boundary.getLeadingTextBoundaryAt(1), 1);
     expect(boundary.getTrailingTextBoundaryAt(1), 3);

     expect(boundary.getLeadingTextBoundaryAt(2), 1);
     expect(boundary.getTrailingTextBoundaryAt(2), 3);

     expect(boundary.getLeadingTextBoundaryAt(3), 3);
     expect(boundary.getTrailingTextBoundaryAt(3), 4);

     expect(boundary.getLeadingTextBoundaryAt(text.length), text.length);
     expect(boundary.getTrailingTextBoundaryAt(text.length), null);
   });

   test('wordBoundary.moveByWordBoundary', () {
     const String text = 'ABC   ABC\n'       // [0, 10)
                         'AÁ    Á\n'         // [10, 20)
                         '         \n'       // [20, 30)
                         'ABC!!!ABC\n'       // [30, 40)
                         '  !ABC !!\n'       // [40, 50)
                         'A  𑗋𑗋 A\n';     // [50, 60)

     final TextPainter textPainter = TextPainter()
       ..textDirection = TextDirection.ltr
       ..text = const TextSpan(text: text)
       ..layout();

     final TextBoundary boundary = textPainter.wordBoundaries.moveByWordBoundary;

     // 4 points to the 2nd whitespace in the first line.
     // Don't break between horizontal spaces and letters/numbers.
     expect(boundary.getLeadingTextBoundaryAt(4), 0);
     expect(boundary.getTrailingTextBoundaryAt(4), 9);

     // Works when words are starting/ending with a combining diacritical mark.
     expect(boundary.getLeadingTextBoundaryAt(14), 10);
     expect(boundary.getTrailingTextBoundaryAt(14), 19);

     // Do break before and after newlines.
     expect(boundary.getLeadingTextBoundaryAt(24), 20);
     expect(boundary.getTrailingTextBoundaryAt(24), 29);

     // Do not break on punctuations.
     expect(boundary.getLeadingTextBoundaryAt(34), 30);
     expect(boundary.getTrailingTextBoundaryAt(34), 39);

     // Ok to break if next to punctuations or separating spaces.
     expect(boundary.getLeadingTextBoundaryAt(44), 43);
     expect(boundary.getTrailingTextBoundaryAt(44), 46);

     // 44 points to a low surrogate of a punctuation.
     expect(boundary.getLeadingTextBoundaryAt(54), 50);
     expect(boundary.getTrailingTextBoundaryAt(54), 59);
   });

   test('line boundary works', () {
     final LineBoundary boundary = LineBoundary(TestTextLayoutMetrics());
     expect(boundary.getLeadingTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3.start);
     expect(boundary.getTrailingTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3.end);
     expect(boundary.getTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3);
   });

   group('paragraph boundary', () {
     test('works for simple cases', () {
       const String textA= 'abcd efg hi\njklmno\npqrstuv';
       const ParagraphBoundary boundaryA = ParagraphBoundary(textA);

       // Position enclosed inside of paragraph, 'abcd efg h|i\n'.
       const int position = 10;

       // The range includes the line terminator.
       expect(boundaryA.getLeadingTextBoundaryAt(position), 0);
       expect(boundaryA.getTrailingTextBoundaryAt(position), 12);

       // This text includes a carriage return followed by a line feed.
       const String textB = 'abcd efg hi\r\njklmno\npqrstuv';
       const ParagraphBoundary boundaryB = ParagraphBoundary(textB);
       expect(boundaryB.getLeadingTextBoundaryAt(position), 0);
       expect(boundaryB.getTrailingTextBoundaryAt(position), 13);

       const String textF = 'Now is the time for\n' // 20
           'all good people\n'                         // 20 + 16 => 36
           'to come to the aid\n'                      // 36 + 19 => 55
           'of their country.';                        // 55 + 17 => 72
       const ParagraphBoundary boundaryF = ParagraphBoundary(textF);
       const int positionF = 11;
       expect(boundaryF.getLeadingTextBoundaryAt(positionF), 0);
       expect(boundaryF.getTrailingTextBoundaryAt(positionF), 20);
     });

     test('works for consecutive line terminators involving CRLF', () {
       const String textI = 'Now is the time for\n' // 20
           'all good people\n\r\n'                         // 20 + 16 => 38
           'to come to the aid\n'                      // 38 + 19 => 57
           'of their country.';                        // 57 + 17 => 74
       const ParagraphBoundary boundaryI = ParagraphBoundary(textI);
       const int positionI = 56;// \n at the end of the third line.
       const int positionJ = 38;// t at beginning of third line.
       const int positionK = 37;// \n at end of second line.
       expect(boundaryI.getLeadingTextBoundaryAt(positionI), 38);
       expect(boundaryI.getTrailingTextBoundaryAt(positionI), 57);
       expect(boundaryI.getLeadingTextBoundaryAt(positionJ), 38);
       expect(boundaryI.getTrailingTextBoundaryAt(positionJ), 57);
       expect(boundaryI.getLeadingTextBoundaryAt(positionK), 36);
       expect(boundaryI.getTrailingTextBoundaryAt(positionK), 38);
     });

     test('works for consecutive line terminators', () {
       const String textI = 'Now is the time for\n' // 20
           'all good people\n\n'                         // 20 + 16 => 37
           'to come to the aid\n'                      // 37 + 19 => 56
           'of their country.';                        // 56 + 17 => 73
       const ParagraphBoundary boundaryI = ParagraphBoundary(textI);
       const int positionI = 55;// \n at the end of the third line.
       const int positionJ = 37;// t at beginning of third line.
       const int positionK = 36;// \n at end of second line.
       expect(boundaryI.getLeadingTextBoundaryAt(positionI), 37);
       expect(boundaryI.getTrailingTextBoundaryAt(positionI), 56);
       expect(boundaryI.getLeadingTextBoundaryAt(positionJ), 37);
       expect(boundaryI.getTrailingTextBoundaryAt(positionJ), 56);
       expect(boundaryI.getLeadingTextBoundaryAt(positionK), 36);
       expect(boundaryI.getTrailingTextBoundaryAt(positionK), 37);
     });

     test('leading boundary works for consecutive CRLF', () {
       // This text includes multiple consecutive carriage returns followed by line feeds (CRLF).
       const String textH = 'abcd efg hi\r\n\r\n\r\n\r\n\r\n\r\n\r\n\n\n\n\n\njklmno\npqrstuv';
       const ParagraphBoundary boundaryH = ParagraphBoundary(textH);
       const int positionH = 18;
       expect(boundaryH.getLeadingTextBoundaryAt(positionH), 17);
       expect(boundaryH.getTrailingTextBoundaryAt(positionH), 19);
     });

     test('trailing boundary works for consecutive CRLF', () {
       // This text includes multiple consecutive carriage returns followed by line feeds (CRLF).
       const String textG = 'abcd efg hi\r\n\n\n\n\n\n\r\n\r\n\r\n\r\n\n\n\n\n\njklmno\npqrstuv';
       const ParagraphBoundary boundaryG = ParagraphBoundary(textG);
       const int positionG = 18;
       expect(boundaryG.getLeadingTextBoundaryAt(positionG), 18);
       expect(boundaryG.getTrailingTextBoundaryAt(positionG), 20);
     });

     test('works when position is between two CRLF', () {
       const String textE = 'abcd efg hi\r\nhello\r\n\n';
       const ParagraphBoundary boundaryE = ParagraphBoundary(textE);
       // Position enclosed inside of paragraph, 'abcd efg hi\r\nhello\r\n\n'.
       const int positionE = 16;
       expect(boundaryE.getLeadingTextBoundaryAt(positionE), 13);
       expect(boundaryE.getTrailingTextBoundaryAt(positionE), 20);
     });

     test('works for multiple consecutive line terminators', () {
       // This text includes multiple consecutive line terminators.
       const String textC = 'abcd efg hi\r\n\n\n\n\n\n\n\n\n\n\n\njklmno\npqrstuv';
       const ParagraphBoundary boundaryC = ParagraphBoundary(textC);
       // Position enclosed inside of paragraph, 'abcd efg hi\r\n\n\n\n\n\n|\n\n\n\n\n\njklmno\npqrstuv'.
       const int positionC = 18;
       expect(boundaryC.getLeadingTextBoundaryAt(positionC), 18);
       expect(boundaryC.getTrailingTextBoundaryAt(positionC), 19);

       const String textD = 'abcd efg hi\r\n\n\n\n';
       const ParagraphBoundary boundaryD = ParagraphBoundary(textD);
       // Position enclosed inside of paragraph, 'abcd efg hi\r\n\n|\n\n'.
       const int positionD = 14;
       expect(boundaryD.getLeadingTextBoundaryAt(positionD), 14);
       expect(boundaryD.getTrailingTextBoundaryAt(positionD), 15);
     });
   });

   test('document boundary works', () {
     const String text = 'abcd efg hi\njklmno\npqrstuv';
     const DocumentBoundary boundary = DocumentBoundary(text);
     expect(boundary, _hasConsistentTextRangeImplementationWithinRange(text.length));

     expect(boundary.getLeadingTextBoundaryAt(-1), null);
     expect(boundary.getTrailingTextBoundaryAt(-1), text.length);

     expect(boundary.getLeadingTextBoundaryAt(0), 0);
     expect(boundary.getTrailingTextBoundaryAt(0), text.length);

     expect(boundary.getLeadingTextBoundaryAt(10), 0);
     expect(boundary.getTrailingTextBoundaryAt(10), text.length);

     expect(boundary.getLeadingTextBoundaryAt(text.length), 0);
     expect(boundary.getTrailingTextBoundaryAt(text.length), null);

     expect(boundary.getLeadingTextBoundaryAt(text.length + 1), 0);
     expect(boundary.getTrailingTextBoundaryAt(text.length + 1), null);
   });
 }

 class TestTextLayoutMetrics extends TextLayoutMetrics {
   static const TextSelection lineAt3 = TextSelection(baseOffset: 0, extentOffset: 10);
   static const TextRange wordBoundaryAt3 = TextRange(start: 4, end: 7);

   @override
   TextSelection getLineAtOffset(TextPosition position) {
     if (position.offset == 3) {
       return lineAt3;
     }
     throw UnimplementedError();
   }

   @override
   TextPosition getTextPositionAbove(TextPosition position) {
     throw UnimplementedError();
   }

   @override
   TextPosition getTextPositionBelow(TextPosition position) {
     throw UnimplementedError();
   }

   @override
   TextRange getWordBoundary(TextPosition position) {
     if (position.offset == 3) {
       return wordBoundaryAt3;
     }
     throw UnimplementedError();
   }
 }
	// Copyright 2014 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'package:flutter/rendering.dart';
	import 'package:flutter/services.dart';
	import 'package:flutter_test/flutter_test.dart';


	class _ConsistentTextRangeImplementationMatcher extends Matcher {
	_ConsistentTextRangeImplementationMatcher(int length)
	: range = TextRange(start: -1, end: length + 1),
	assert(length >= 0);

	final TextRange range;
	@override
	Description describe(Description description) {
	return description.add('The implementation of TextBoundary.getTextBoundaryAt is consistent with its other methods.');
	}

	@override
	Description describeMismatch(dynamic item, Description mismatchDescription, Map<dynamic, dynamic> matchState, bool verbose) {
	final TextBoundary boundary = matchState['textBoundary'] as TextBoundary;
	final int position = matchState['position'] as int;
	final int leading = boundary.getLeadingTextBoundaryAt(position) ?? -1;
	final int trailing = boundary.getTrailingTextBoundaryAt(position) ?? -1;

	return mismatchDescription.add(
	'at position $position, expected ${TextRange(start: leading, end: trailing)} but got ${boundary.getTextBoundaryAt(position)}',
	);
	}

	@override
	bool matches(dynamic item, Map<dynamic, dynamic> matchState) {
	for (int i = range.start; i <= range.end; i++) {
	final int? leading = (item as TextBoundary).getLeadingTextBoundaryAt(i);
	final int? trailing = item.getTrailingTextBoundaryAt(i);
	final TextRange boundary = item.getTextBoundaryAt(i);
	final bool consistent = boundary.start == (leading ?? -1) && boundary.end == (trailing ?? -1);
	if (!consistent) {
	matchState['textBoundary'] = item;
	matchState['position'] = i;
	return false;
	}
	}
	return true;
	}
	}

	Matcher _hasConsistentTextRangeImplementationWithinRange(int length) => _ConsistentTextRangeImplementationMatcher(length);

	void main() {
	test('Character boundary works', () {
	const CharacterBoundary boundary = CharacterBoundary('abc');
	expect(boundary, _hasConsistentTextRangeImplementationWithinRange(3));

	expect(boundary.getLeadingTextBoundaryAt(-1), null);
	expect(boundary.getTrailingTextBoundaryAt(-1), 0);

	expect(boundary.getLeadingTextBoundaryAt(0), 0);
	expect(boundary.getTrailingTextBoundaryAt(0), 1);

	expect(boundary.getLeadingTextBoundaryAt(1), 1);
	expect(boundary.getTrailingTextBoundaryAt(1), 2);

	expect(boundary.getLeadingTextBoundaryAt(2), 2);
	expect(boundary.getTrailingTextBoundaryAt(2), 3);

	expect(boundary.getLeadingTextBoundaryAt(3), 3);
	expect(boundary.getTrailingTextBoundaryAt(3), null);

	expect(boundary.getLeadingTextBoundaryAt(4), 3);
	expect(boundary.getTrailingTextBoundaryAt(4), null);
	});

	test('Character boundary works with grapheme', () {
	const String text = 'a❄︎c';
	const CharacterBoundary boundary = CharacterBoundary(text);
	expect(boundary, _hasConsistentTextRangeImplementationWithinRange(text.length));

	expect(boundary.getLeadingTextBoundaryAt(-1), null);
	expect(boundary.getTrailingTextBoundaryAt(-1), 0);

	expect(boundary.getLeadingTextBoundaryAt(0), 0);
	expect(boundary.getTrailingTextBoundaryAt(0), 1);

	// The `❄` takes two character length.
	expect(boundary.getLeadingTextBoundaryAt(1), 1);
	expect(boundary.getTrailingTextBoundaryAt(1), 3);

	expect(boundary.getLeadingTextBoundaryAt(2), 1);
	expect(boundary.getTrailingTextBoundaryAt(2), 3);

	expect(boundary.getLeadingTextBoundaryAt(3), 3);
	expect(boundary.getTrailingTextBoundaryAt(3), 4);

	expect(boundary.getLeadingTextBoundaryAt(text.length), text.length);
	expect(boundary.getTrailingTextBoundaryAt(text.length), null);
	});

	test('wordBoundary.moveByWordBoundary', () {
	const String text = 'ABC ABC\n' // [0, 10)
	'AÁ Á\n' // [10, 20)
	' \n' // [20, 30)
	'ABC!!!ABC\n' // [30, 40)
	' !ABC !!\n' // [40, 50)
	'A 𑗋𑗋 A\n'; // [50, 60)

	final TextPainter textPainter = TextPainter()
	..textDirection = TextDirection.ltr
	..text = const TextSpan(text: text)
	..layout();

	final TextBoundary boundary = textPainter.wordBoundaries.moveByWordBoundary;

	// 4 points to the 2nd whitespace in the first line.
	// Don't break between horizontal spaces and letters/numbers.
	expect(boundary.getLeadingTextBoundaryAt(4), 0);
	expect(boundary.getTrailingTextBoundaryAt(4), 9);

	// Works when words are starting/ending with a combining diacritical mark.
	expect(boundary.getLeadingTextBoundaryAt(14), 10);
	expect(boundary.getTrailingTextBoundaryAt(14), 19);

	// Do break before and after newlines.
	expect(boundary.getLeadingTextBoundaryAt(24), 20);
	expect(boundary.getTrailingTextBoundaryAt(24), 29);

	// Do not break on punctuations.
	expect(boundary.getLeadingTextBoundaryAt(34), 30);
	expect(boundary.getTrailingTextBoundaryAt(34), 39);

	// Ok to break if next to punctuations or separating spaces.
	expect(boundary.getLeadingTextBoundaryAt(44), 43);
	expect(boundary.getTrailingTextBoundaryAt(44), 46);

	// 44 points to a low surrogate of a punctuation.
	expect(boundary.getLeadingTextBoundaryAt(54), 50);
	expect(boundary.getTrailingTextBoundaryAt(54), 59);
	});

	test('line boundary works', () {
	final LineBoundary boundary = LineBoundary(TestTextLayoutMetrics());
	expect(boundary.getLeadingTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3.start);
	expect(boundary.getTrailingTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3.end);
	expect(boundary.getTextBoundaryAt(3), TestTextLayoutMetrics.lineAt3);
	});

	group('paragraph boundary', () {
	test('works for simple cases', () {
	const String textA= 'abcd efg hi\njklmno\npqrstuv';
	const ParagraphBoundary boundaryA = ParagraphBoundary(textA);

	// Position enclosed inside of paragraph, 'abcd efg h\|i\n'.
	const int position = 10;

	// The range includes the line terminator.
	expect(boundaryA.getLeadingTextBoundaryAt(position), 0);
	expect(boundaryA.getTrailingTextBoundaryAt(position), 12);

	// This text includes a carriage return followed by a line feed.
	const String textB = 'abcd efg hi\r\njklmno\npqrstuv';
	const ParagraphBoundary boundaryB = ParagraphBoundary(textB);
	expect(boundaryB.getLeadingTextBoundaryAt(position), 0);
	expect(boundaryB.getTrailingTextBoundaryAt(position), 13);

	const String textF = 'Now is the time for\n' // 20
	'all good people\n' // 20 + 16 => 36
	'to come to the aid\n' // 36 + 19 => 55
	'of their country.'; // 55 + 17 => 72
	const ParagraphBoundary boundaryF = ParagraphBoundary(textF);
	const int positionF = 11;
	expect(boundaryF.getLeadingTextBoundaryAt(positionF), 0);
	expect(boundaryF.getTrailingTextBoundaryAt(positionF), 20);
	});

	test('works for consecutive line terminators involving CRLF', () {
	const String textI = 'Now is the time for\n' // 20
	'all good people\n\r\n' // 20 + 16 => 38
	'to come to the aid\n' // 38 + 19 => 57
	'of their country.'; // 57 + 17 => 74
	const ParagraphBoundary boundaryI = ParagraphBoundary(textI);
	const int positionI = 56;// \n at the end of the third line.
	const int positionJ = 38;// t at beginning of third line.
	const int positionK = 37;// \n at end of second line.
	expect(boundaryI.getLeadingTextBoundaryAt(positionI), 38);
	expect(boundaryI.getTrailingTextBoundaryAt(positionI), 57);
	expect(boundaryI.getLeadingTextBoundaryAt(positionJ), 38);
	expect(boundaryI.getTrailingTextBoundaryAt(positionJ), 57);
	expect(boundaryI.getLeadingTextBoundaryAt(positionK), 36);
	expect(boundaryI.getTrailingTextBoundaryAt(positionK), 38);
	});

	test('works for consecutive line terminators', () {
	const String textI = 'Now is the time for\n' // 20
	'all good people\n\n' // 20 + 16 => 37
	'to come to the aid\n' // 37 + 19 => 56
	'of their country.'; // 56 + 17 => 73
	const ParagraphBoundary boundaryI = ParagraphBoundary(textI);
	const int positionI = 55;// \n at the end of the third line.
	const int positionJ = 37;// t at beginning of third line.
	const int positionK = 36;// \n at end of second line.
	expect(boundaryI.getLeadingTextBoundaryAt(positionI), 37);
	expect(boundaryI.getTrailingTextBoundaryAt(positionI), 56);
	expect(boundaryI.getLeadingTextBoundaryAt(positionJ), 37);
	expect(boundaryI.getTrailingTextBoundaryAt(positionJ), 56);
	expect(boundaryI.getLeadingTextBoundaryAt(positionK), 36);
	expect(boundaryI.getTrailingTextBoundaryAt(positionK), 37);
	});

	test('leading boundary works for consecutive CRLF', () {
	// This text includes multiple consecutive carriage returns followed by line feeds (CRLF).
	const String textH = 'abcd efg hi\r\n\r\n\r\n\r\n\r\n\r\n\r\n\n\n\n\n\njklmno\npqrstuv';
	const ParagraphBoundary boundaryH = ParagraphBoundary(textH);
	const int positionH = 18;
	expect(boundaryH.getLeadingTextBoundaryAt(positionH), 17);
	expect(boundaryH.getTrailingTextBoundaryAt(positionH), 19);
	});

	test('trailing boundary works for consecutive CRLF', () {
	// This text includes multiple consecutive carriage returns followed by line feeds (CRLF).
	const String textG = 'abcd efg hi\r\n\n\n\n\n\n\r\n\r\n\r\n\r\n\n\n\n\n\njklmno\npqrstuv';
	const ParagraphBoundary boundaryG = ParagraphBoundary(textG);
	const int positionG = 18;
	expect(boundaryG.getLeadingTextBoundaryAt(positionG), 18);
	expect(boundaryG.getTrailingTextBoundaryAt(positionG), 20);
	});

	test('works when position is between two CRLF', () {
	const String textE = 'abcd efg hi\r\nhello\r\n\n';
	const ParagraphBoundary boundaryE = ParagraphBoundary(textE);
	// Position enclosed inside of paragraph, 'abcd efg hi\r\nhello\r\n\n'.
	const int positionE = 16;
	expect(boundaryE.getLeadingTextBoundaryAt(positionE), 13);
	expect(boundaryE.getTrailingTextBoundaryAt(positionE), 20);
	});

	test('works for multiple consecutive line terminators', () {
	// This text includes multiple consecutive line terminators.
	const String textC = 'abcd efg hi\r\n\n\n\n\n\n\n\n\n\n\n\njklmno\npqrstuv';
	const ParagraphBoundary boundaryC = ParagraphBoundary(textC);
	// Position enclosed inside of paragraph, 'abcd efg hi\r\n\n\n\n\n\n\|\n\n\n\n\n\njklmno\npqrstuv'.
	const int positionC = 18;
	expect(boundaryC.getLeadingTextBoundaryAt(positionC), 18);
	expect(boundaryC.getTrailingTextBoundaryAt(positionC), 19);

	const String textD = 'abcd efg hi\r\n\n\n\n';
	const ParagraphBoundary boundaryD = ParagraphBoundary(textD);
	// Position enclosed inside of paragraph, 'abcd efg hi\r\n\n\|\n\n'.
	const int positionD = 14;
	expect(boundaryD.getLeadingTextBoundaryAt(positionD), 14);
	expect(boundaryD.getTrailingTextBoundaryAt(positionD), 15);
	});
	});

	test('document boundary works', () {
	const String text = 'abcd efg hi\njklmno\npqrstuv';
	const DocumentBoundary boundary = DocumentBoundary(text);
	expect(boundary, _hasConsistentTextRangeImplementationWithinRange(text.length));

	expect(boundary.getLeadingTextBoundaryAt(-1), null);
	expect(boundary.getTrailingTextBoundaryAt(-1), text.length);

	expect(boundary.getLeadingTextBoundaryAt(0), 0);
	expect(boundary.getTrailingTextBoundaryAt(0), text.length);

	expect(boundary.getLeadingTextBoundaryAt(10), 0);
	expect(boundary.getTrailingTextBoundaryAt(10), text.length);

	expect(boundary.getLeadingTextBoundaryAt(text.length), 0);
	expect(boundary.getTrailingTextBoundaryAt(text.length), null);

	expect(boundary.getLeadingTextBoundaryAt(text.length + 1), 0);
	expect(boundary.getTrailingTextBoundaryAt(text.length + 1), null);
	});
	}

	class TestTextLayoutMetrics extends TextLayoutMetrics {
	static const TextSelection lineAt3 = TextSelection(baseOffset: 0, extentOffset: 10);
	static const TextRange wordBoundaryAt3 = TextRange(start: 4, end: 7);

	@override
	TextSelection getLineAtOffset(TextPosition position) {
	if (position.offset == 3) {
	return lineAt3;
	}
	throw UnimplementedError();
	}

	@override
	TextPosition getTextPositionAbove(TextPosition position) {
	throw UnimplementedError();
	}

	@override
	TextPosition getTextPositionBelow(TextPosition position) {
	throw UnimplementedError();
	}

	@override
	TextRange getWordBoundary(TextPosition position) {
	if (position.offset == 3) {
	return wordBoundaryAt3;
	}
	throw UnimplementedError();
	}
	}