Address the review

core/common/src/DateTimePeriod.kt

@@ -465,7 +465,7 @@ public class DatePeriod internal constructor(
 
     /** The number of nanoseconds in this period. Always equal to zero. */
     override val nanoseconds: Int get() = 0
-    override val totalNanoseconds: Long get() = 0
+    internal override val totalNanoseconds: Long get() = 0
 
     public companion object {
         /**
@@ -495,9 +495,9 @@ public class DatePeriod internal constructor(
 public fun String.toDatePeriod(): DatePeriod = DatePeriod.parse(this)
 
 private class DateTimePeriodImpl(
-    override val totalMonths: Long,
+    internal override val totalMonths: Long,
     override val days: Int,
-    override val totalNanoseconds: Long,
+    internal override val totalNanoseconds: Long,
 ) : DateTimePeriod()
 
 private fun totalMonths(years: Int, months: Int): Long = (years.toLong() * 12 + months.toLong()).also {

core/common/src/LocalDate.kt

@@ -20,7 +20,7 @@ import kotlinx.serialization.Serializable
  * is `2020-08-31` everywhere): see various [LocalDate.plus] and [LocalDate.minus] functions, as well
  * as [LocalDate.periodUntil] and various other [*until][LocalDate.daysUntil] functions.
  *
- * The range of supported years is at least is enough to represent dates of all instants between
+ * The range of supported years is at least enough to represent dates of all instants between
  * [Instant.DISTANT_PAST] and [Instant.DISTANT_FUTURE].
  *
  * ### Arithmetic operations
@@ -168,7 +168,7 @@ public expect class LocalDate : Comparable<LocalDate> {
      * The components [monthNumber] and [dayOfMonth] are 1-based.
      *
      * The supported ranges of components:
-     * - [year] the range is at least is enough to represent dates of all instants between
+     * - [year] the range is at least enough to represent dates of all instants between
      *          [Instant.DISTANT_PAST] and [Instant.DISTANT_FUTURE]
      * - [monthNumber] `1..12`
      * - [dayOfMonth] `1..31`, the upper bound can be less, depending on the month

core/common/test/InstantTest.kt

@@ -313,9 +313,7 @@ class InstantTest {
                 val diff2 = date1.periodUntil(date2)
 
                 if (diff1 != diff2)
-                    throw AssertionError(
-                        "start: $instant1, end: $instant2, diff by instants: $diff1, diff by dates: $diff2"
-                    )
+                    fail("start: $instant1, end: $instant2, diff by instants: $diff1, diff by dates: $diff2")
             }
         }
     }
@@ -560,10 +558,13 @@ class InstantRangeTest {
             assertArithmeticFails("$instant") { instant.plus(Long.MIN_VALUE, DateTimeUnit.YEAR, UTC) }
         }
         for (instant in smallInstants) {
-            instant.plus(2 * Int.MAX_VALUE.toLong(), DateTimeUnit.DAY, UTC)
-            instant.plus(2 * Int.MIN_VALUE.toLong(), DateTimeUnit.DAY, UTC)
-            instant.plus(2 * Int.MAX_VALUE.toLong(), DateTimeUnit.MONTH, UTC)
-            instant.plus(2 * Int.MIN_VALUE.toLong(), DateTimeUnit.MONTH, UTC)
+            fun roundTrip(value: Long, unit: DateTimeUnit) {
+                assertEquals(instant, instant.plus(value, unit, UTC).minus(value, unit, UTC))
+            }
+            roundTrip(2L * Int.MAX_VALUE, DateTimeUnit.DAY)
+            roundTrip(2L * Int.MIN_VALUE, DateTimeUnit.DAY)
+            roundTrip(2L * Int.MAX_VALUE, DateTimeUnit.MONTH)
+            roundTrip(2L * Int.MIN_VALUE, DateTimeUnit.MONTH)
         }
         // Overflowing a LocalDateTime in input
         maxValidInstant.plus(-1, DateTimeUnit.NANOSECOND, UTC)

settings.gradle.kts

@@ -21,5 +21,5 @@ project(":timezones/full").name = "kotlinx-datetime-zoneinfo"
 include(":serialization")
 project(":serialization").name = "kotlinx-datetime-serialization"
 include(":js-without-timezones")
-project(":js-without-timezones").name = "kotlinx-datetime-js-without-timezones"
+project(":js-without-timezones").name = "kotlinx-datetime-js-test-without-timezones"
 include(":benchmarks")