add auto-highlighting of selected/updated code

tests/unit/application/State/Code/Position/CodePosition.spec.ts

@@ -0,0 +1,54 @@
+import { CodePosition } from '@/application/State/Code/Position/CodePosition';
+import 'mocha';
+import { expect } from 'chai';
+
+describe('CodePosition', () => {
+    describe('ctor', () => {
+        it('creates with valid parameters', () => {
+            // arrange
+            const startPosition = 0;
+            const endPosition = 5;
+            // act
+            const sut = new CodePosition(startPosition, endPosition);
+            // assert
+            expect(sut.startLine).to.equal(startPosition);
+            expect(sut.endLine).to.equal(endPosition);
+        });
+        it('throws with negative start position', () => {
+            // arrange
+            const startPosition = -1;
+            const endPosition = 5;
+            // act
+            const getSut = () => new CodePosition(startPosition, endPosition);
+            // assert
+            expect(getSut).to.throw('Code cannot start in a negative line');
+        });
+        it('throws with negative end position', () => {
+            // arrange
+            const startPosition = 1;
+            const endPosition = -5;
+            // act
+            const getSut = () => new CodePosition(startPosition, endPosition);
+            // assert
+            expect(getSut).to.throw('Code cannot end in a negative line');
+        });
+        it('throws when start and end position is same', () => {
+            // arrange
+            const startPosition = 0;
+            const endPosition = 0;
+            // act
+            const getSut = () => new CodePosition(startPosition, endPosition);
+            // assert
+            expect(getSut).to.throw('Empty code');
+        });
+        it('throws when ends before start', () => {
+            // arrange
+            const startPosition = 3;
+            const endPosition = 2;
+            // act
+            const getSut = () => new CodePosition(startPosition, endPosition);
+            // assert
+            expect(getSut).to.throw('End line cannot be less than start line');
+        });
+    });
+});