Merge pull request #148 from sialcasa/#134_fluentViewLoader_mocking

Add a unit test that shows how you can mock the view loader.

mvvmfx/src/test/java/de/saxsys/mvvmfx/internal/viewloader/MockableViewLoaderTest.java

@@ -0,0 +1,68 @@
+package de.saxsys.mvvmfx.internal.viewloader;
+
+import de.saxsys.mvvmfx.ViewTuple;
+import org.junit.Test;
+
+import de.saxsys.mvvmfx.FluentViewLoader;
+import de.saxsys.mvvmfx.internal.viewloader.example.TestFxmlView;
+import de.saxsys.mvvmfx.internal.viewloader.example.TestViewModel;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * The purpose of this test is to check that mocking of view loading is possible. 
+ * 
+ * In theory loading a view is something that involves the environment of the application and therefore
+ * goes beyond the scope of a Unit-Test. So in most cases the developer shouldn't need to test the view loading with a unit test.
+ * 
+ * The MVVM pattern supports this by saying that the loading of another view is done in the View component and 
+ * <strong>not</strong> in the ViewModel and the View is not a target of unit-tests in MVVM. 
+ *
+ * Only the conditions under which a view has to be loaded should be defined (and unit-tested) in the ViewModel.
+ * 
+ * The consequence of these statements is that testing the loading of a view isn't a first-class problem with MVVM.
+ * It should only be needed in some rare corner-cases. 
+ * 
+ * The API of MvvmFX reflects this: The methods in {@link FluentViewLoader} to load a view are static for a better usability. 
+ * They are not optimized for unit-testing and mocking.
+ * 
+ * This test will show that mocking the loading process is still possible when with a little bit of extra code. 
+ * 
+ */
+public class MockableViewLoaderTest {
+
+	public static class MyApplication {
+
+		public FluentViewLoader.FxmlViewStep<TestFxmlView, TestViewModel> builder =
+				FluentViewLoader.fxmlView(TestFxmlView.class);
+
+
+		public ViewTuple<TestFxmlView, TestViewModel> viewTuple;
+
+		public void methodToTest() {
+			viewTuple = builder.load();
+		}
+	}
+
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void test() {
+		MyApplication application = new MyApplication();
+
+		FluentViewLoader.FxmlViewStep mock = mock(FluentViewLoader.FxmlViewStep.class);
+
+		ViewTuple<TestFxmlView, TestViewModel> viewTupleMock = mock(ViewTuple.class);
+		when(mock.load()).thenReturn(viewTupleMock);
+
+
+		application.builder = mock;
+		application.methodToTest();
+
+		assertThat(application.viewTuple).isNotNull().isSameAs(viewTupleMock);
+	}
+
+
+}