diff --git a/tests/phpunit/tests/functions/wpTimezoneOverrideOffset.php b/tests/phpunit/tests/functions/wpTimezoneOverrideOffset.php
new file mode 100644
index 0000000000..3b92e8c6fe
--- /dev/null
+++ b/tests/phpunit/tests/functions/wpTimezoneOverrideOffset.php
@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * Tests for the wp_timezone_override_offset function.
+ *
+ * @group Functions.php
+ *
+ * @covers ::wp_timezone_override_offset
+ */
+class Tests_Functions_wpTimezoneOverrideOffset extends WP_UnitTestCase {
+	/**
+	 * @ticket 59980
+	 */
+	public function test_wp_timezone_override_offset_with_no_timezone_string_option_set() {
+		$this->assertSame( '', get_option( 'timezone_string' ) );
+		$this->assertFalse( wp_timezone_override_offset() );
+	}
+
+	/**
+	 * @ticket 59980
+	 */
+	public function test_wp_timezone_override_offset_with_bad_option_set() {
+		update_option( 'timezone_string', 'BAD_TIME_ZONE' );
+		$this->assertFalse( wp_timezone_override_offset() );
+	}
+
+	/**
+	 * @ticket 59980
+	 */
+	public function test_wp_timezone_override_offset_with_UTC_option_set() {
+		update_option( 'timezone_string', 'UTC' );
+		$offset = wp_timezone_override_offset();
+		$this->assertSame( 0.0, $offset );
+	}
+
+	/**
+	 * @ticket 59980
+	 */
+	public function test_wp_timezone_override_offset_with_EST_option_set() {
+		update_option( 'timezone_string', 'EST' );
+		$offset = wp_timezone_override_offset();
+		$this->assertSame( -5.0, $offset );
+	}
+
+	/**
+	 * @ticket 59980
+	 */
+	public function test_wp_timezone_override_offset_with_NST_option_set() {
+		update_option( 'timezone_string', 'America/St_Johns' );
+		$offset = wp_timezone_override_offset();
+		$this->assertSame( -3.5, $offset );
+	}
+}