Bael 1366 dagger2 (#4288)

* BAEL-1366-dagger2: Added Dagger 2 example and test case. Added dependency and Dagger compiler plugin to pom.

dagger/src/test/java/com/baeldung/dagger/intro/DaggerUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.dagger.intro;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Unit test for building a {@link Car} using Dagger.
+ * 
+ * @author Donato Rimenti
+ *
+ */
+public class DaggerUnitTest {
+	
+	/**
+	 * Builds two {@link Car} and checks that the fields are injected correctly.
+	 */
+	@Test
+	public void givenGeneratedComponent_whenBuildingCar_thenDependenciesInjected() {
+		VehiclesComponent component = DaggerVehiclesComponent.create();
+		
+		Car carOne = component.buildCar();
+		Car carTwo = component.buildCar();
+		
+		Assert.assertNotNull(carOne);
+		Assert.assertNotNull(carTwo);
+		Assert.assertNotNull(carOne.getEngine());
+		Assert.assertNotNull(carTwo.getEngine());
+		Assert.assertNotNull(carOne.getBrand());
+		Assert.assertNotNull(carTwo.getBrand());
+		Assert.assertNotEquals(carOne.getEngine(), carTwo.getEngine());
+		Assert.assertEquals(carOne.getBrand(), carTwo.getBrand());
+	}
+
+}