Add IsEven function and update README.md

src/main/kotlin/codecollection/snippets/numbers/IsEven.kt

@@ -0,0 +1,3 @@
+package codecollection.snippets.numbers
+
+fun isEven(n: Int): Boolean = n % 2 == 0

src/main/kotlin/codecollection/snippets/numbers/README.md

@@ -11,5 +11,6 @@ Each snippet is implemented as an extension function or utility method, and test
 | File                             | Description                           |
 |----------------------------------|---------------------------------------|
 | [`DigitCount.kt`](DigitCount.kt) | Returns the number of digits in an integer  |
-| _More coming soon..._            |                                       |
+| [`IsEven.kt`](IsEven.kt)         | Returns true if the given numberis Even |
+| _More coming soon..._                            |                                       |
 

src/test/kotlin/codecollection/snippets/numbers/IsEvenTest.kt

@@ -0,0 +1,23 @@
+package codecollection.snippets.numbers
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class IsEvenTest {
+
+    @Test
+    fun `should return true for even numbers`() {
+        assertTrue(isEven(0))
+        assertTrue(isEven(2))
+        assertTrue(isEven(-4))
+        assertTrue(isEven(100))
+    }
+
+    @Test
+    fun `should return false for odd numbers`() {
+        assertFalse(isEven(1))
+        assertFalse(isEven(-3))
+        assertFalse(isEven(99))
+    }
+}