SCALA-53 sorting (#36)

* sorting example

* use given when then format

Author: ldrygala

core-scala/src/test/scala/com/baeldung/scala/SortingUnitTest.scala

@@ -0,0 +1,76 @@
+package com.baeldung.scala
+
+import org.junit.Test
+import org.scalatest.{Matchers, WordSpec}
+
+class SortingUnitTest extends WordSpec with Matchers {
+
+  case class User(name: String, age: Int) extends Ordered[User] {
+    override def compare(that: User): Int =
+      java.lang.Integer.compare(age, that.age)
+  }
+
+  val users = List(
+    User("Mike", 43),
+    User("Mike", 16),
+    User("Kelly", 21)
+  )
+
+  @Test
+  def givenUsers_whenSorted_thenSortUsingOrdered(): Unit = {
+    users.sorted shouldBe List(
+      User("Mike", 16),
+      User("Kelly", 21),
+      User("Mike", 43),
+    )
+  }
+
+  @Test
+  def givenUsers_whenSorted_thenSortUsingOrdering(): Unit = {
+    implicit val userOrdering: Ordering[User] = Ordering.by(_.age)
+
+    users.sorted shouldBe List(
+      User("Mike", 16),
+      User("Kelly", 21),
+      User("Mike", 43),
+    )
+  }
+
+  @Test
+  def givenUsers_whenSorted_thenSortUsingReverseOrdering(): Unit = {
+    implicit val userOrdering: Ordering[User] = Ordering.by[User, Int](_.age).reverse
+
+    users.sorted shouldBe List(
+      User("Mike", 43),
+      User("Kelly", 21),
+      User("Mike", 16),
+    )
+  }
+
+  @Test
+  def givenUsers_whenSortBy_thenSortByField(): Unit = {
+    users.sortBy(_.name) shouldBe List(
+      User("Kelly", 21),
+      User("Mike", 43),
+      User("Mike", 16),
+    )
+  }
+
+  @Test
+  def givenUsers_whenSortWith_thenSortWithCompareFunction(): Unit = {
+    users.sortWith(_.age > _.age) shouldBe List(
+      User("Mike", 43),
+      User("Kelly", 21),
+      User("Mike", 16),
+    )
+  }
+
+  @Test
+  def givenUsers_whenSortBy_thenSortByMultipleFields(): Unit = {
+    users.sortBy(u => (u.name, u.age)) shouldBe List(
+      User("Kelly", 21),
+      User("Mike", 16),
+      User("Mike", 43),
+    )
+  }
+}