Added a few unit tests for kotlin operator examples.

core-kotlin/src/main/kotlin/com/baeldung/operators/Money.kt

@@ -1,3 +1,5 @@
+package com.baeldung.operators
+
 import java.math.BigDecimal
 
 enum class Currency {

core-kotlin/src/main/kotlin/com/baeldung/operators/Page.kt

@@ -1,3 +1,5 @@
+package com.baeldung.operators
+
 interface Page<T> {
     fun pageNumber(): Int
     fun pageSize(): Int

core-kotlin/src/main/kotlin/com/baeldung/operators/Point.kt

@@ -1,3 +1,5 @@
+package com.baeldung.operators
+
 data class Point(val x: Int, val y: Int)
 
 operator fun Point.unaryMinus() = Point(-x, -y)
@@ -14,7 +16,7 @@ operator fun Point.times(factor: Int): Point = Point(x * factor, y * factor)
 operator fun Int.times(point: Point): Point = Point(point.x * this, point.y * this)
 
 class Shape {
-    private val points = mutableListOf<Point>()
+    val points = mutableListOf<Point>()
 
     operator fun Point.unaryPlus() {
         points.add(this)

core-kotlin/src/main/kotlin/com/baeldung/operators/Utils.kt

@@ -1,3 +1,5 @@
+package com.baeldung.operators
+
 import java.math.BigInteger
 
 operator fun <T> MutableCollection<T>.plusAssign(element: T) {