Add tests

src/test/java/at/pcgamingfreaks/mkvaudiosubtitlechanger/util/DateUtilsTest.java

@@ -0,0 +1,21 @@
+package at.pcgamingfreaks.mkvaudiosubtitlechanger.util;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Date;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class DateUtilsTest {
+
+    @Test
+    void convert() {
+        Date expectedDate = new Date(0);
+        String expectedString = "01.01.1970-01:00:00";
+
+        assertEquals(expectedDate, DateUtils.convert(0));
+        assertEquals(expectedDate, DateUtils.convert(expectedString, expectedDate));
+        assertEquals(expectedDate, DateUtils.convert("1234;15", expectedDate));
+        assertEquals(expectedString, DateUtils.convert(expectedDate));
+    }
+}