diff --git a/tests/phpunit/tests/formatting/HumanTimeDiff.php b/tests/phpunit/tests/formatting/HumanTimeDiff.php
new file mode 100644
index 0000000000..da1ad2dcfc
--- /dev/null
+++ b/tests/phpunit/tests/formatting/HumanTimeDiff.php
@@ -0,0 +1,69 @@
+<?php
+
+/**
+ * @group formatting
+ * @ticket 38773
+ */
+class Tests_Formatting_HumanTimeDiff extends WP_UnitTestCase {
+
+	/**
+	 * @group formatting
+	 * @ticket 38773
+	 * @dataProvider data_test_human_time_diff
+	 */
+	function test_human_time_diff( $expected, $stopdate, $message ) {
+		$startdate = new DateTime( '2016-01-01 12:00:00' );
+		$this->assertEquals( $expected, human_time_diff( $startdate->format( 'U' ), $stopdate->format( 'U' ) ), $message );
+	}
+
+	// Data for test_human_time_diff.
+	function data_test_human_time_diff() {
+		return array(
+			array(
+				'5 mins',
+				new DateTime( '2016-01-01 12:05:00' ),
+				'Test a difference of 5 minutes.',
+			),
+			array(
+				'1 hour',
+				new DateTime( '2016-01-01 13:00:00' ),
+				'Test a difference of 1 hour.',
+			),
+			array(
+				'2 days',
+				new DateTime( '2016-01-03 12:00:00' ),
+				'Test a difference of 2 days.',
+			),
+			array(
+				'2 hours',
+				new DateTime( '2016-01-01 14:29:59' ),
+				'Test a difference of 2 hours, 29 minutes and 59 seconds  - should round down to 2 hours.',
+			),
+			array(
+				'3 hours',
+				new DateTime( '2016-01-01 14:30:00' ),
+				'Test a difference of 2 hours and 30 minutes - should round up to 3 hours.',
+			),
+			array(
+				'2 months',
+				new DateTime( '2016-02-15 12:00:00' ),
+				'Test a difference of 1 month and 15 days - should round up to 2 months.',
+			),
+			array(
+				'1 month',
+				new DateTime( '2016-02-14 12:00:00' ),
+				'Test a difference of 1 month and 14 days - should round down to 1 month.',
+			),
+			array(
+				'3 years',
+				new DateTime( '2018-07-02 12:00:00' ),
+				'Test a difference of 2 years 6 months and 1 day, should round up to 3 years.',
+			),
+			array(
+				'2 years',
+				new DateTime( '2018-07-01 12:00:00' ),
+				'Test a difference of 2 years 6 months, should round down to 2 years.',
+			),
+		);
+	}
+}