BAEL-1733 (#4417)

* BAEL-1733

* naming conventions settled

* createManifestFile method added

* remove accidentally created MANIFEST.MF file from the project root flder

core-java/src/test/java/com/baeldung/manifest/ExecuteJarFileUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.manifest;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class ExecuteJarFileUnitTest {
+
+    private static final String ERROR_MESSAGE = "no main manifest attribute, in example.jar\n";
+    private static final String SUCCESS_MESSAGE = "AppExample executed!\n";
+
+    @Test
+    public final void givenDefaultManifest_whenManifestAttributeIsNotPresent_thenGetErrorMessage() {
+        String output = ExecuteJarFile.executeJarWithoutManifestAttribute();
+        assertEquals(ERROR_MESSAGE, output);
+    }
+
+    @Test
+    public final void givenCustomManifest_whenManifestAttributeIsPresent_thenGetSuccessMessage() {
+        String output = ExecuteJarFile.executeJarWithManifestAttribute();
+        assertEquals(SUCCESS_MESSAGE, output);
+    }
+
+}