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) {

core-kotlin/src/test/kotlin/com/baeldung/operators/PageTest.kt

@@ -0,0 +1,28 @@
+package com.baeldung.operators
+
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class PageTest {
+
+    private val page = PageImpl(1, 10, "Java", "Kotlin", "Scala")
+
+    @Test
+    fun `Get convention should work as expected`() {
+        assertEquals(page[1], "Kotlin")
+        assertEquals(page[1, 3], listOf("Kotlin", "Scala"))
+    }
+
+    @Test
+    fun `In convention should work on a page as expected`() {
+        assertTrue("Kotlin" in page)
+    }
+
+}
+
+private class PageImpl<T>(val page: Int, val size: Int, vararg val elements: T) : Page<T> {
+    override fun pageNumber(): Int = page
+    override fun pageSize(): Int = size
+    override fun elements(): MutableList<T> = mutableListOf(*elements)
+}

core-kotlin/src/test/kotlin/com/baeldung/operators/PointTest.kt

@@ -0,0 +1,48 @@
+package com.baeldung.operators
+
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class PointTest {
+
+    private val p1 = Point(1, 2)
+    private val p2 = Point(2, 3)
+
+    @Test
+    fun `We should be able to add two points together using +`() {
+        assertEquals(p1 + p2, Point(3, 5))
+    }
+
+    @Test
+    fun `We shoud be able to subtract one point from another using -`() {
+        assertEquals(p1 - p2, Point(-1, -1))
+    }
+
+    @Test
+    fun `We should be able to multiply two points together with *`() {
+        assertEquals(p1 * p2, Point(2, 6))
+    }
+
+    @Test
+    fun `We should be able to divide one point by another`() {
+        assertEquals(p1 / p2, Point(0, 0))
+    }
+
+    @Test
+    fun `We should be able to scale a point by an integral factor`() {
+        assertEquals(p1 * 2, Point(2, 4))
+        assertEquals(2 * p1, Point(2, 4))
+    }
+
+    @Test
+    fun `We should be able to add points to an empty shape`() {
+        val line = shape {
+            +Point(0, 0)
+            +Point(1, 3)
+        }
+
+        assertTrue(Point(0, 0) in line.points)
+        assertTrue(Point(1, 3) in line.points)
+    }
+}