Added sample code for eachCount and eachCountTo methods

Author: yadavan88

core-kotlin-modules/core-kotlin-collections-6/src/test/kotlin/com/baeldung/eachCountMethods/EachCountMethodsUnitTest.kt

@@ -0,0 +1,34 @@
+package com.baeldung.eachCountMethods
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+class EachCountMethodsUnitTest {
+    @Test
+    fun `given a list of flights eachCount method should create a count per airline`() {
+        val flights = listOf("EK060", "EK531", "LH7", "LH1030", "DL47", "AI120")
+        val flightCount = flights.groupingBy { it.take(2) }.eachCount()
+        val expectedMap = mapOf("EK" to 2, "LH" to 2, "DL" to 1, "AI" to 1)
+        assertEquals(expectedMap, flightCount)
+    }
+
+    @Test
+    fun `given a list of flights, use groupBy and count to implement eachCount logic`() {
+        val flights = listOf("EK060", "EK531", "LH7", "LH1030", "DL47", "AI120")
+        val flightCount = flights.groupBy { it.take(2) }.mapValues { it.value.count() }
+        val expectedMap = mapOf("EK" to 2, "LH" to 2, "DL" to 1, "AI" to 1)
+        assertEquals(expectedMap, flightCount)
+    }
+
+    @Test
+    fun `given a list of flights eachCountTo method should create a count per airline`() {
+        val flights = listOf("EK060", "EK531", "LH7", "LH1030", "DL47", "AI120")
+        val flightCount = flights.groupingBy { it.take(2) }.eachCount().toMutableMap()
+        val expectedMap = mutableMapOf("EK" to 2, "LH" to 2, "DL" to 1, "AI" to 1)
+        assertEquals(expectedMap, flightCount)
+        val moreFlights = listOf("EK061", "AI435")
+        moreFlights.groupingBy { it.take(2) }.eachCountTo(flightCount)
+        val expectedMapAfterMoreFlights = mutableMapOf("EK" to 3, "LH" to 2, "DL" to 1, "AI" to 2)
+        assertEquals(expectedMapAfterMoreFlights, flightCount)
+    }
+}