Merge branch 'upstream-master' into scala-463

# Conflicts:
#	build.sbt

Author: Matteo Di Pirro

build.sbt

@@ -284,6 +284,24 @@ lazy val scala_libraries_3 = (project in file("scala-libraries-3"))
     libraryDependencies += "com.lihaoyi" %% "os-lib" % "0.8.1"
   )
 
+lazy val scala_libraries_os = (project in file("scala-libraries-os"))
+  .settings(
+    name := "scala-libraries",
+    libraryDependencies += "org.scalatest" %% "scalatest" % "3.1.2" % Test,
+    libraryDependencies ++= Seq(
+      "org.apache.logging.log4j" %% "log4j-api-scala" % "12.0",
+      "org.apache.logging.log4j" % "log4j-core" % "2.13.0" % Runtime
+    ),
+    libraryDependencies += "com.lihaoyi" %% "os-lib" % "0.8.1"
+  )
+
+lazy val scala_libraries_4 = (project in file("scala-libraries-4"))
+  .settings(
+    name := "scala-libraries-4",
+    libraryDependencies += "com.lihaoyi" %% "utest" % "0.8.1" % "test",
+    testFrameworks += new TestFramework("utest.runner.Framework")
+  )
+
 lazy val scala_libraries_4 = (project in file("scala-libraries-4"))
   .settings(
     name := "scala-libraries",

scala-core-collection-2/README.md

@@ -4,3 +4,4 @@
 - [Get a List Item by Index in Scala](https://www.baeldung.com/scala/list-get-item-by-index)
 - [Guide to Scala ListSet](https://www.baeldung.com/scala/listset)
 - [Guide to Scala ListMap](https://www.baeldung.com/scala/listmap)
+- [How to Flatten Collections in Scala](https://www.baeldung.com/scala/flattening-collections)

scala-core-collections/src/main/scala/com/baeldung/scala/mergemaps/CombineIterables.scala

@@ -0,0 +1,12 @@
+package com.baeldung.scala.mergemaps
+
+object CombineIterables {
+
+  def combineIterables[K, V](
+    a: Map[K, Iterable[V]],
+    b: Map[K, Iterable[V]]
+  ): Map[K, Iterable[V]] = {
+    a ++ b.map { case (k, v) => k -> (v ++ a.getOrElse(k, Iterable.empty)) }
+  }
+
+}

scala-core-collections/src/test/scala/com/baedung/scala/mergemaps/MergeMapsUnitTest.scala

@@ -0,0 +1,25 @@
+package com.baedung.scala.mergemaps
+
+import com.baeldung.scala.mergemaps.CombineIterables
+import org.scalatest.{FlatSpec, Matchers}
+
+class MergeMapsUnitTest extends FlatSpec with Matchers {
+
+  "++ operator" should "merge maps preferring duplicates from second map" in {
+    val firstMap = Map(1 -> "Apple", 5 -> "Banana", 3 -> "Orange");
+    val secondMap = Map(5 -> "Pear", 4 -> "Cherry");
+
+    firstMap ++ secondMap should equal(
+      Map(1 -> "Apple", 5 -> "Pear", 3 -> "Orange", 4 -> "Cherry")
+    )
+  }
+
+  "combineIterables" should "combine values for duplicate keys" in {
+    val firstMap = Map(1 -> List(1, 2, 3))
+    val secondMap = Map(1 -> List(4, 5))
+
+    CombineIterables.combineIterables(firstMap, secondMap) should equal(
+      Map(1 -> List(4, 5, 1, 2, 3))
+    )
+  }
+}

scala-libraries-3/README.md

@@ -9,5 +9,4 @@
 - [A Guide to the Scala Retry Library](https://www.baeldung.com/scala/retry-library)
 - [Introduction to Lightbend Config](https://www.baeldung.com/scala/lightbend-config)
 - [Introduction to Apache Log4j in Scala](https://www.baeldung.com/scala/apache-log4j)
-- [Introduction to Tapir](https://www.baeldung.com/scala/tapir)
-- [How to Execute OS Commands in Scala Using os-lib](https://www.baeldung.com/scala/os-lib)
+- [Introduction to Tapir](https://www.baeldung.com/scala/tapir)

scala-libraries-4/README.md

@@ -0,0 +1,2 @@
+## Relevant Articles
+- [Introduction to uTest](https://www.baeldung.com/scala/utest-intro)

scala-libraries-4/src/test/scala/com/baeldung/scala/utest/AsyncTest.scala

@@ -0,0 +1,16 @@
+package com.baeldung.scala.utest
+
+import utest._
+
+import scala.concurrent.Future
+import scala.concurrent.ExecutionContext.Implicits.global
+
+object AsyncTest extends TestSuite {
+  def getFromDB(): Future[Int] = Future { 42 }
+
+  override def tests: Tests = Tests {
+    test("get something from database") {
+      getFromDB().map(v => assert(v == 42))
+    }
+  }
+}

scala-libraries-4/src/test/scala/com/baeldung/scala/utest/BeforeAfterTest.scala

@@ -0,0 +1,18 @@
+package com.baeldung.scala.utest
+
+import utest._
+
+object BeforeAfterTest extends TestSuite {
+  println("This is executed before the tests")
+  override def utestAfterAll() = {
+    println("This method will be executed after all the tests")
+  }
+  override def tests: Tests = Tests {
+    test("simple test") {
+      assert(1 == 1)
+    }
+    test("simple test 2") {
+      assert(2 == 2)
+    }
+  }
+}

scala-libraries-4/src/test/scala/com/baeldung/scala/utest/ExceptionHandling.scala

@@ -0,0 +1,15 @@
+package com.baeldung.scala.utest
+
+import utest._
+
+object ExceptionHandling extends TestSuite {
+  override def tests: Tests = Tests {
+    def funnyMethod: String = throw new RuntimeException("Uh oh...")
+    test("Handle an exception") {
+      val ex = intercept[RuntimeException] {
+        funnyMethod
+      }
+      assert(ex.getMessage == "Uh oh...")
+    }
+  }
+}

scala-libraries-4/src/test/scala/com/baeldung/scala/utest/NestedTest.scala

@@ -0,0 +1,24 @@
+package com.baeldung.scala.utest
+
+import utest._
+
+object NestedTest extends TestSuite {
+  override def tests: Tests = Tests {
+    test("outer test") - {
+      val list = List(1, 2)
+      println("This is an outer level of the test.")
+      test("inner test 1") - {
+        val list2 = List(10, 20)
+        list.zip(list2) ==> List((1, 10), (2, 20))
+      }
+      test("inner test 2") - {
+        val str = List("a", "b")
+        list.zip(str) ==> List((1, "a"), (2, "b"))
+      }
+    }
+    test("outer test 2") - {
+      println("there is no nesting level here")
+      assert(true)
+    }
+  }
+}