Add test to check tree prop (#15)

Author: Hoang Chau Khanh

package.json

@@ -54,6 +54,7 @@
   },
   "jest": {
     "automock": false,
+    "testRegex": "test/.*\\.js$",
     "coverageDirectory": "coverage/",
     "collectCoverage": true
   }

__tests__/react-tree-test.js renamed to test/react-tree-test.js

@@ -25,4 +25,12 @@ describe('ReactTree', () => {
 
     expect(handleOnChanged).toBeCalled();
   });
+
+  it('should show error when tree is not object or array', () => {
+    const reactTree = TestUtils.renderIntoDocument(
+      <ReactTree tree={1} />
+    );
+
+    expect(ReactTree.propTypes.tree).toBeDefined();
+  });
 });