Add armstrong-numbers exercise

config.json

@@ -105,6 +105,17 @@
         "Mathematics"
       ]
     },
+    {
+      "uuid": "2bd9ab9e-ecc4-4331-984d-8e5f15f775b4",
+      "slug": "armstrong-numbers",
+      "core": false,
+      "unlocked_by": "leap",
+      "difficulty": 2,
+      "topics": [
+        "Integers",
+        "Mathematics"
+      ]
+    },
     {
       "uuid": "5a31217f-02fd-4be4-b64f-7a93f36f5140",
       "slug": "hamming",

exercises/armstrong-numbers/build.sbt

@@ -0,0 +1,3 @@
+scalaVersion := "2.12.1"
+
+libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.1" % "test"

exercises/armstrong-numbers/example.scala

@@ -0,0 +1,7 @@
+object ArmstrongNumbers {
+  def isArmstrongNumber(i: Int): Boolean = {
+    val s = i.toString
+    val power = s.length
+    i == s.toStream.foldLeft(0.0)((acc, c) => acc + math.pow(c.asDigit, power))
+  }
+}

exercises/armstrong-numbers/src/test/scala/ArmstrongNumbersTest.scala

@@ -0,0 +1,44 @@
+import org.scalatest.{Matchers, FunSuite}
+
+/** @version 1.0.0 */
+class ArmstrongNumbersTest extends FunSuite with Matchers {
+
+  test("Single digit numbers are Armstrong numbers") {
+    ArmstrongNumbers.isArmstrongNumber(5) should be (true)
+  }
+
+  test("There are no 2 digit Armstrong numbers") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(10) should be (false)
+  }
+
+  test("Three digit number that is an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(153) should be (true)
+  }
+
+  test("Three digit number that is not an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(100) should be (false)
+  }
+
+  test("Four digit number that is an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(9474) should be (true)
+  }
+
+  test("Four digit number that is not an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(9475) should be (false)
+  }
+
+  test("Seven digit number that is an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(9926315) should be (true)
+  }
+
+  test("Seven digit number that is not an Armstrong number") {
+    pending
+    ArmstrongNumbers.isArmstrongNumber(9926314) should be (false)
+  }
+}

testgen/src/main/scala/ArmstrongNumbersTestGenerator.scala

@@ -0,0 +1,33 @@
+import java.io.File
+
+import testgen.TestSuiteBuilder._
+import testgen._
+
+object ArmstrongNumbersTestGenerator {
+  def main(args: Array[String]): Unit = {
+    val file = new File("src/main/resources/armstrong-numbers.json")
+
+    def toString(expected: CanonicalDataParser.Expected): String = {
+      expected match {
+        case Right(b: Boolean) => b.toString
+        case _ => throw new IllegalStateException()
+      }
+    }
+
+    def fromLabeledTestFromInput(argNames: String*): ToTestCaseData =
+      withLabeledTest { sut =>
+        labeledTest =>
+          val args = sutArgsFromInput(labeledTest.result, argNames: _*)
+          val property = labeledTest.property
+          val sutCall =
+            s"""$sut.$property($args)"""
+          val expected = toString(labeledTest.expected)
+          TestCaseData(labeledTest.description, sutCall, expected)
+      }
+
+    val code = TestSuiteBuilder.build(file, fromLabeledTestFromInput("number"))
+    println(s"-------------")
+    println(code)
+    println(s"-------------")
+  }
+}