added ability to revert (#21)

tests/unit/application/State/Selection/SelectedScript.spec.ts

@@ -0,0 +1,28 @@
+import { ScriptStub } from './../../../stubs/ScriptStub';
+import { SelectedScript } from '@/application/State/Selection/SelectedScript';
+import 'mocha';
+import { expect } from 'chai';
+
+describe('SelectedScript', () => {
+    it('id is same as script id', () => {
+        // arrange
+        const expectedId = 'scriptId';
+        const script = new ScriptStub(expectedId);
+        const sut = new SelectedScript(script, false);
+        // act
+        const actualId = sut.id;
+        // assert
+        expect(actualId).to.equal(expectedId);
+    });
+    it('throws when revert is true for irreversible script', () => {
+        // arrange
+        const expectedId = 'scriptId';
+        const script = new ScriptStub(expectedId)
+            .withRevertCode(undefined);
+        // act
+        function construct() { new SelectedScript(script, true); } // tslint:disable-line:no-unused-expression
+        // assert
+        expect(construct).to.throw('cannot revert an irreversible script');
+    });
+
+});