[KTLN-789] Add Samples (Baeldung#725)

* [KTLN-789] Add Samples

* [KTLN-789] Add Samples

* [KTLN-789] Add Samples

core-kotlin-modules/core-kotlin-9/src/test/kotlin/com/baeldung/md5/Md5UnitTest.kt

@@ -0,0 +1,40 @@
+package com.baeldung.md5
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import java.io.File
+import java.security.MessageDigest
+
+class Md5UnitTest {
+    @Test
+    fun `Calling extension md5 should return a md5 hash`() {
+        val stringToBeHashed = "Hello, Baeldung!"
+        val expectedHash = "6469a4ea9e2753755f5120beb51587f8"
+        val calculatedHash = stringToBeHashed.md5()
+
+        assertEquals(expectedHash, calculatedHash)
+    }
+
+    @Test
+    fun `Calling extension md5 on a file should return a md5 hash`() {
+        val fileToBeHashed = File("src/test/resources/test_md5.txt")
+        val expectedHash = "ef948f943cdba8514ed5aab7592a904d"
+        val calculatedHash = fileToBeHashed.md5()
+
+        assertEquals(expectedHash, calculatedHash)
+    }
+}
+
+@OptIn(ExperimentalStdlibApi::class)
+fun String.md5(): String {
+    val md = MessageDigest.getInstance("MD5")
+    val digest = md.digest(this.toByteArray())
+    return digest.toHexString()
+}
+
+@OptIn(ExperimentalStdlibApi::class)
+fun File.md5(): String {
+    val md = MessageDigest.getInstance("MD5")
+    val digest = md.digest(this.readBytes())
+    return digest.toHexString()
+}

core-kotlin-modules/core-kotlin-9/src/test/resources/test_md5.txt

@@ -0,0 +1 @@
+Hello, Baeldung! I'm a file!