js - enable showModal e2e test and create dismissModal e2e test

playground/e2e/app.test.js

     expect(elementByLabel('React Native Navigation!')).toBeVisible();
   });
 
-  xit('show modal', () => {
+  it('show modal', () => {
     elementByLabel('Show Modal').tap();
     expect(elementByLabel('Modal screen')).toBeVisible();
   });
+  
+  it('dismiss modal', () => {
+    elementByLabel('Show Modal').tap();
+    expect(elementByLabel('Modal screen')).toBeVisible();
+    elementByLabel('Dismiss Modal').tap();
+    expect(elementByLabel('React Native Navigation!')).toBeVisible();
+  });
 });
 
 describe('reload app', () => {

playground/src/containers/SimpleScreen.js

     super(props);
     this.onClickPop = this.onClickPop.bind(this);
     this.onClickPush = this.onClickPush.bind(this);
+    this.onClickShowModal = this.onClickShowModal.bind(this);
     this.onClickDismissModal = this.onClickDismissModal.bind(this);
   }
 
         {this.renderTextFromFunctionInProps()}
         <Button title="Push" onPress={this.onClickPush} />
         <Button title="Pop" onPress={this.onClickPop} />
+        <Button title="Show Mddal" onPress={this.onClickPop} />
         <Button title="Dismiss Modal" onPress={this.onClickDismissModal} />
       </View>
     );
       }
     });
   }
+  
+  onClickShowModal() {
+    Navigation.showModal({
+      name: 'navigation.playground.SimpleScreen',
+      passProps: {
+        text: 'Modal screen'
+      }
+    });
+  }
 
   onClickDismissModal() {
     Navigation.dismissModal(this.props.id);