https://jira.baeldung.com/browse/BAEL-7268

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/unixtime/UnixTimeUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.unixtime;
+
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.Instant;
+import java.util.Date;
+
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
+import org.junit.jupiter.api.Test;
+
+public class UnixTimeUnitTest {
+
+    @Test
+    public void givenCurrentTimeUsingDateApi_whenConvertedToUnixTime_thenConsistent() {
+        long marginOfError = 1L;
+        Date date = new Date();
+        long longTime = date.getTime() / 1000L;
+
+        for (int i = 0; i < 10; i++) {
+            long unixTime = System.currentTimeMillis() / 1000L;
+            assertEquals(longTime, unixTime, marginOfError);
+        }
+    }
+
+    @Test
+    public void givenCurrentTimeUsingInstantNow_whenConvertedToUnixTime_thenConsistent() {
+        long marginOfError = 1L;
+        long longTime = Instant.now().getEpochSecond();
+
+        for (int i = 0; i < 10; i++) {
+            long unixTime = System.currentTimeMillis() / 1000L;
+            assertEquals(longTime, unixTime, marginOfError);
+        }
+    }
+
+    @Test
+    public void givenCurrentTimeUsingJodaTime_whenConvertedToUnixTime_thenConsistent() {
+        long marginOfError = 1L;
+        DateTime dateTime = DateTime.now(DateTimeZone.UTC);
+        long longTime = dateTime.getMillis() / 1000L;
+
+        for (int i = 0; i < 10; i++) {
+            long unixTime = System.currentTimeMillis() / 1000L;
+            assertEquals(longTime, unixTime, marginOfError);
+        }
+    }
+
+}