SCALA-36 (#8764)

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

@@ -0,0 +1,82 @@
+package com.baeldung.scala
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+
+class HigherOrderFunctionsExamplesUnitTest {
+
+  @Test
+  def whenCallingMapWithAnonymousFunction_thenTransformationIsApplied() = {
+    val expected = Seq("sir Alex Ferguson", "sir Bobby Charlton", "sir Frank Lampard")
+
+    val names = Seq("Alex Ferguson", "Bobby Charlton", "Frank Lampard")
+    val sirNames = names.map(name => "sir " + name)
+
+    assertEquals(expected, sirNames)
+  }
+
+  @Test
+  def whenCallingMapWithDefined_thenTransformationIsApplied() = {
+    val expected = Seq("sir Alex Ferguson", "sir Bobby Charlton", "sir Frank Lampard")
+
+    val names = Seq("Alex Ferguson", "Bobby Charlton", "Frank Lampard")
+
+    def prefixWithSir(name: String) = "sir " + name
+    val sirNames = names.map(prefixWithSir)
+
+    assertEquals(expected, sirNames)
+  }
+
+  @Test
+  def whenCallingFilter_thenUnecessaryElementsAreRemoved() = {
+    val expected = Seq("John O'Shea", "John Hartson")
+
+    val names = Seq("John O'Shea", "Aiden McGeady", "John Hartson")
+    val johns = names.filter(name => name.matches("^John .*"))
+
+    assertEquals(expected, johns)
+  }
+
+  @Test
+  def whenCallingReduce_thenProperSumIsCalculated() = {
+    val expected = 2750
+
+    val earnings = Seq(1000, 1300, 450)
+    val sumEarnings = earnings.reduce((acc, x) => acc + x)
+
+    assertEquals(expected, sumEarnings)
+  }
+
+  @Test
+  def whenCallingFold_thenNumberOfWordsShouldBeCalculated() = {
+    val expected = 6
+
+    val strings = Seq("bunch of words", "just me", "it")
+    val sumEarnings = strings.foldLeft(0)((acc, x) => acc + x.split(" ").size)
+
+    assertEquals(expected, sumEarnings)
+  }
+
+  @Test
+  def whenCallingOwnHigherOrderFunction_thenProperFunctionIsReturned() = {
+    def mathOperation(name: String): (Int, Int) => Int = (x: Int, y: Int) => {
+      name match {
+        case "addition" => x + y
+        case "multiplication" => x * y
+        case "division" => x/y
+        case "subtraction" => x - y
+      }
+    }
+
+    def add: (Int, Int) => Int = mathOperation("addition")
+    def mul: (Int, Int) => Int = mathOperation("multiplication")
+    def div: (Int, Int) => Int = mathOperation("division")
+    def sub: (Int, Int) => Int = mathOperation("subtraction")
+
+    assertEquals(15, add(10, 5))
+    assertEquals(50, mul(10, 5))
+    assertEquals(2, div(10, 5))
+    assertEquals(5, sub(10, 5))
+  }
+}