add a test to test events

test_apps/test_app/app/contracts/simple_storage.sol

@@ -13,6 +13,7 @@ library Assert {
 contract SimpleStorage is Ownable {
   uint public storedData;
   address public registar;
+  event EventOnSet2(bool passed, string message);
 
   function() public payable { }
 
@@ -30,6 +31,7 @@ contract SimpleStorage is Ownable {
 
   function set2(uint x, uint unusedGiveWarning) public onlyOwner {
     storedData = x;
+    emit EventOnSet2(true, "hi");
   }
 
   function get() public view returns (uint retVal) {

test_apps/test_app/test/simple_storage_spec.js

@@ -37,4 +37,15 @@ contract("SimpleStorage", function () {
     assert.strictEqual(SimpleStorage.options.address, SimpleStorage.address);
   });
 
+  it('listens to events', function (done) {
+    SimpleStorage.once('EventOnSet2', async function(error, _result){
+      assert.strictEqual(error, null);
+      let result = await SimpleStorage.methods.get().call();
+      assert.strictEqual(parseInt(result, 10), 150);
+      done();
+    });
+
+    SimpleStorage.methods.set2(150, 100).send();
+  });
+
 });