Lock clock when testing date time formatters

This is done to fix the failing date formatters test. The reason it fails is, since one of the date format we have doesn't have year attached to it "MM-dd HH:mm:ss", it picks it from the current system time. 

The expected value I provided was for year 2023, but since the year is now 2024, the tests has started to fail. So locking the clock (which I should've done from the start) to a specific date time, so that the tests are reproducible.

core/network/src/androidMain/kotlin/dev/sasikanth/rss/reader/core/network/parser/DateTimeFormatters.android.kt

@@ -16,13 +16,15 @@
 
 package dev.sasikanth.rss.reader.core.network.parser
 
-import java.time.LocalDateTime
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 import java.time.temporal.ChronoField
 import java.time.temporal.UnsupportedTemporalTypeException
+import kotlinx.datetime.Clock
 import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toJavaLocalDateTime
 import kotlinx.datetime.toJavaZoneId
+import kotlinx.datetime.toLocalDateTime
 
 private val dateFormatters =
   listOf(
@@ -45,13 +47,15 @@ private val dateFormatters =
   )
 
 @Throws(DateTimeFormatException::class)
-internal actual fun String?.dateStringToEpochMillis(): Long? {
+internal actual fun String?.dateStringToEpochMillis(clock: Clock): Long? {
   if (this.isNullOrBlank()) return null
 
+  val currentDate =
+    clock.now().toLocalDateTime(TimeZone.currentSystemDefault()).toJavaLocalDateTime()
+
   for (dateFormatter in dateFormatters) {
     try {
       val parsedValue = dateFormatter.parse(this)
-      val currentDate = LocalDateTime.now()
 
       val year =
         try {

core/network/src/commonMain/kotlin/dev/sasikanth/rss/reader/core/network/parser/DateTimeFormatters.kt

@@ -16,6 +16,8 @@
 
 package dev.sasikanth.rss.reader.core.network.parser
 
-internal expect fun String?.dateStringToEpochMillis(): Long?
+import kotlinx.datetime.Clock
+
+internal expect fun String?.dateStringToEpochMillis(clock: Clock = Clock.System): Long?
 
 data class DateTimeFormatException(val exception: Exception) : Exception()

core/network/src/commonTest/kotlin/dev/sasikanth/rss/reader/core/network/parser/DateTimeFormattersTest.kt

@@ -72,7 +72,7 @@ class DateTimeFormattersTest {
     val epochMillis =
       dates.map {
         try {
-          it.dateStringToEpochMillis()
+          it.dateStringToEpochMillis(clock = TestClock)
         } catch (e: Exception) {
           // no-op
         }
@@ -88,7 +88,7 @@ class DateTimeFormattersTest {
     val invalidDate = "Invalid date"
 
     // when
-    val epochMillis = invalidDate.dateStringToEpochMillis()
+    val epochMillis = invalidDate.dateStringToEpochMillis(clock = TestClock)
 
     // then
     assertEquals(null, epochMillis)

core/network/src/commonTest/kotlin/dev/sasikanth/rss/reader/core/network/parser/TestClock.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2024 Sasikanth Miriyampalli
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dev.sasikanth.rss.reader.core.network.parser
+
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.Month
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toInstant
+
+object TestClock : Clock {
+
+  override fun now(): Instant {
+    return LocalDateTime(
+        year = 2023,
+        month = Month.JANUARY,
+        dayOfMonth = 1,
+        hour = 8,
+        minute = 0,
+      )
+      .toInstant(TimeZone.UTC)
+  }
+}

core/network/src/iosMain/kotlin/dev/sasikanth/rss/reader/core/network/parser/DateTimeFormatters.ios.kt

@@ -16,7 +16,9 @@
 
 package dev.sasikanth.rss.reader.core.network.parser
 
+import kotlinx.datetime.Clock
 import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toNSDate
 import kotlinx.datetime.toNSTimeZone
 import platform.Foundation.NSCalendar
 import platform.Foundation.NSCalendarIdentifierGregorian
@@ -27,7 +29,6 @@ import platform.Foundation.NSCalendarUnitMonth
 import platform.Foundation.NSCalendarUnitNanosecond
 import platform.Foundation.NSCalendarUnitSecond
 import platform.Foundation.NSCalendarUnitYear
-import platform.Foundation.NSDate
 import platform.Foundation.NSDateFormatter
 import platform.Foundation.NSLocale
 import platform.Foundation.timeIntervalSince1970
@@ -68,7 +69,7 @@ private val dateFormatters =
   )
 
 @Throws(DateTimeFormatException::class)
-internal actual fun String?.dateStringToEpochMillis(): Long? {
+internal actual fun String?.dateStringToEpochMillis(clock: Clock): Long? {
   if (this.isNullOrBlank()) return null
 
   try {
@@ -78,7 +79,7 @@ internal actual fun String?.dateStringToEpochMillis(): Long? {
       }
 
     if (date != null) {
-      val currentDate = NSDate()
+      val currentDate = clock.now().toNSDate()
       val calendar = NSCalendar(NSCalendarIdentifierGregorian)
 
       val currentYear = calendar.component(NSCalendarUnitYear, currentDate)