tests and fixes in week work

src/commonTest/kotlin/dev/inmo/krontab/utils/WeekDaysTest.kt

@@ -0,0 +1,38 @@
+package dev.inmo.krontab.utils
+
+import com.soywiz.klock.*
+import dev.inmo.krontab.builder.buildSchedule
+import kotlin.math.ceil
+import kotlin.test.*
+
+class WeekDaysTest {
+    @Test
+    fun testThatWeekDaysSchedulingWorks() {
+        val startDateTime = DateTime.now().startOfDay
+        val weekDay = startDateTime.dayOfWeek.index0
+        val testDays = 400
+        val scheduler = buildSchedule {
+            dayOfWeek {
+                at(weekDay)
+            }
+            years {
+                at(startDateTime.yearInt)
+            }
+        }
+        runTest {
+            for (day in 0 until testDays) {
+                val currentDateTime = startDateTime + day.days
+                val next = scheduler.next(currentDateTime)
+                val expected = when {
+                    day % 7 == 0 -> currentDateTime
+                    else -> startDateTime + ceil(day.toFloat() / 7).weeks
+                }
+                if (expected.yearInt != startDateTime.yearInt) {
+                    assertNull(next)
+                } else {
+                    assertEquals(expected, next)
+                }
+            }
+        }
+    }
+}