Issue #57: Add test: BetweenDayOfWeekValueGenerator does not work for…

… the first day of a month in some cases.

src/test/java/com/cronutils/model/time/ExecutionTimeCustomDefinitionIntegrationTest.java

@@ -114,4 +114,35 @@ public void testCronExpressionEveryTwoHoursSlash2() {
 
         assertTrue(DateTime.parse("2015-08-28T14:00:00.000-03:00").compareTo(ExecutionTime.forCron(cron).nextExecution(startDateTime)) == 0);
     }
+
+    /**
+     * Test for issue #57
+     * https://github.com/jmrozanec/cron-utils/issues/57
+     * Reported case: BetweenDayOfWeekValueGenerator does not work for the first day of a month in some cases.
+     * Expected: first day of month should be returned ok
+     */
+    public void testCronExpressionBetweenDayOfWeekValueGeneratorCorrectFirstDayOfMonth() {
+        CronDefinition cronDefinition = CronDefinitionBuilder.defineCron()
+                .withMinutes().and()
+                .withHours().and()
+                .withDayOfMonth()
+                .supportsL().supportsW()
+                .and()
+                .withMonth().and()
+                .withDayOfWeek()
+                .withMondayDoWValue(1)
+                .withValidRange(1, 7)
+                .supportsHash().supportsL()
+                .and()
+                .withYear().and()
+                .lastFieldOptional().instance();
+
+        CronParser parser = new CronParser(cronDefinition);
+        Cron cron = parser.parse("30 3 * * MON-FRI");
+        DateTime sameDayBeforeEventStartDateTime = DateTime.parse("1970-01-01T00:00:00.000-03:00");
+        System.out.println(ExecutionTime.forCron(cron).nextExecution(sameDayBeforeEventStartDateTime));
+        assertEquals(1, ExecutionTime.forCron(cron).nextExecution(sameDayBeforeEventStartDateTime).getDayOfMonth());
+        DateTime sameDayAfterEventStartDateTime = DateTime.parse("1970-01-01T12:00:00.000-03:00");
+        assertEquals(2, ExecutionTime.forCron(cron).nextExecution(sameDayAfterEventStartDateTime).getDayOfMonth());
+    }
 }