KTLN-547: Unit tests for Sorting String dates

Signed-off-by: Diego Torres <[email protected]>

Author: diegotorrespy

core-kotlin-modules/core-kotlin-collections-6/src/test/kotlin/com/baeldung/listofdates/SortingListOfStringDatesTest.kt

@@ -0,0 +1,56 @@
+package com.baeldung.listofdates
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+import kotlin.test.assertNotNull
+
+class SortingListOfStringDatesTest {
+
+    @Test
+    fun `given a list of string dates when sorting with sortedDescending then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy")
+        val sortedDates = dates.map { LocalDate.parse(it, formatter) }
+                .sortedDescending()
+                .map { it.format(formatter) }
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+
+    @Test
+    fun `given a list of string dates when sorting with sortedByDescending then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val dateTimeFormatter: DateTimeFormatter = DateTimeFormatter.ofPattern("dd-MM-yyyy")
+
+        val sortedDates = dates.sortedByDescending {
+            LocalDate.parse(it, dateTimeFormatter)
+        }
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+
+    @Test
+    fun `given a list of string dates when sorting using custom comparator then a sorted list is generated`() {
+        val dates = listOf("31-12-2023", "01-01-2023", "15-06-2023")
+
+        val sortedDates = dates.sortedWith(compareByDescending {
+            val (day, month, year) = it.split("-")
+            "$year-$month-$day"
+        })
+
+        val expectedSortedDates = listOf("31-12-2023", "15-06-2023", "01-01-2023")
+
+        assertNotNull(sortedDates)
+        assertEquals(sortedDates, expectedSortedDates)
+    }
+}