Add test for Friday 13th crontab failure

Added test for Friday 13th trigger, i.e. an uncommon crontab expression.
With the new CronExpression in place, this failure does not occur
anymore.

Closes gh-21574

Author: poutsma

spring-context/src/test/java/org/springframework/scheduling/support/CronExpressionTests.java

@@ -25,6 +25,7 @@
 
 import org.junit.jupiter.api.Test;
 
+import static java.time.DayOfWeek.FRIDAY;
 import static java.time.DayOfWeek.MONDAY;
 import static java.time.DayOfWeek.TUESDAY;
 import static java.time.DayOfWeek.WEDNESDAY;
@@ -444,4 +445,21 @@ public void fixedDays() {
 		assertThat(actual.getDayOfWeek()).isEqualTo(WEDNESDAY);
 	}
 
+	@Test
+	void friday13th() {
+		CronExpression expression = CronExpression.parse("0 0 0 13 * FRI");
+
+		LocalDateTime last = LocalDateTime.of(2018, 7, 31, 11, 47, 14);
+		LocalDateTime actual = expression.next(last);
+		assertThat(actual).isNotNull();
+		assertThat(actual.getDayOfWeek()).isEqualTo(FRIDAY);
+		assertThat(actual.getDayOfMonth()).isEqualTo(13);
+
+		last = actual;
+		actual = expression.next(last);
+		assertThat(actual).isNotNull();
+		assertThat(actual.getDayOfWeek()).isEqualTo(FRIDAY);
+		assertThat(actual.getDayOfMonth()).isEqualTo(13);
+	}
+
 }