Add tests

Author: gspencergoog

testing/dart/text_test.dart

@@ -24,4 +24,59 @@ void main() {
       expect(FontWeight.lerp(FontWeight.w400, null, 1), equals(FontWeight.w400));
     });
   });
+  group('TextRange', () {
+    test('empty ranges are correct', () {
+      const TextRange range = TextRange(start: -1, end: -1);
+      expect(range, equals(const TextRange.collapsed(-1)));
+      expect(range, equals(TextRange.empty));
+    });
+    test('isValid works', () {
+      expect(TextRange.empty.isValid, isFalse);
+      expect(const TextRange(start: 0, end: 0).isValid, isTrue);
+      expect(const TextRange(start: 0, end: 10).isValid, isTrue);
+      expect(const TextRange(start: 10, end: 10).isValid, isTrue);
+      expect(const TextRange(start: -1, end: 10).isValid, isFalse);
+      expect(const TextRange(start: 10, end: 0).isValid, isTrue);
+      expect(const TextRange(start: 10, end: -1).isValid, isFalse);
+    });
+    test('isCollapsed works', () {
+      expect(TextRange.empty.isCollapsed, isTrue);
+      expect(const TextRange(start: 0, end: 0).isCollapsed, isTrue);
+      expect(const TextRange(start: 0, end: 10).isCollapsed, isFalse);
+      expect(const TextRange(start: 10, end: 10).isCollapsed, isTrue);
+      expect(const TextRange(start: -1, end: 10).isCollapsed, isFalse);
+      expect(const TextRange(start: 10, end: 0).isCollapsed, isFalse);
+      expect(const TextRange(start: 10, end: -1).isCollapsed, isFalse);
+    });
+    test('isNormalized works', () {
+      expect(TextRange.empty.isNormalized, isTrue);
+      expect(const TextRange(start: 0, end: 0).isNormalized, isTrue);
+      expect(const TextRange(start: 0, end: 10).isNormalized, isTrue);
+      expect(const TextRange(start: 10, end: 10).isNormalized, isTrue);
+      expect(const TextRange(start: -1, end: 10).isNormalized, isTrue);
+      expect(const TextRange(start: 10, end: 0).isNormalized, isFalse);
+      expect(const TextRange(start: 10, end: -1).isNormalized, isFalse);
+    });
+    test('textBefore works', () {
+      expect(const TextRange(start: 0, end: 0).textBefore('hello'), isEmpty);
+      expect(const TextRange(start: 1, end: 1).textBefore('hello'), equals('h'));
+      expect(const TextRange(start: 1, end: 2).textBefore('hello'), equals('h'));
+      expect(const TextRange(start: 5, end: 5).textBefore('hello'), equals('hello'));
+      expect(const TextRange(start: 0, end: 5).textBefore('hello'), isEmpty);
+    });
+    test('textAfter works', () {
+      expect(const TextRange(start: 0, end: 0).textAfter('hello'), equals('hello'));
+      expect(const TextRange(start: 1, end: 1).textAfter('hello'), equals('ello'));
+      expect(const TextRange(start: 1, end: 2).textAfter('hello'), equals('llo'));
+      expect(const TextRange(start: 5, end: 5).textAfter('hello'), isEmpty);
+      expect(const TextRange(start: 0, end: 5).textAfter('hello'), isEmpty);
+    });
+    test('textInside works', () {
+      expect(const TextRange(start: 0, end: 0).textInside('hello'), isEmpty);
+      expect(const TextRange(start: 1, end: 1).textInside('hello'), isEmpty);
+      expect(const TextRange(start: 1, end: 2).textInside('hello'), equals('e'));
+      expect(const TextRange(start: 5, end: 5).textInside('hello'), isEmpty);
+      expect(const TextRange(start: 0, end: 5).textInside('hello'), equals('hello'));
+    });
+  });
 }