Change implementation of Test.dateString

lib/TestTemplate.js

@@ -144,7 +144,7 @@ class TestTemplate {
 			.setBody(
 				`New test added for class ${c.name}:\n` +
 				`Test name: ${this.name}\n` +
-				`Test date: ${t.dateString}\n` +
+				`Test date: ${t.getDateString()}\n` +
 				`Maximum mark: ${this.maxMark}`
 			);