protractor expect method returns an error while everything is working correctly

I'm using a protractor to test an angular application. I was trying to get a text and compare it, but I got this weird error!

I have this line of code :

expect(warning.getText()).toEqual('The GLAccount or Number already exists.');

And the test failed with this message:

Expected ['The GLAccount or Number already exists.'] to equal 'The GLAccount or Number already exists.'.