The test does a GET after the PUT and the expected response is an array with the single issue that was updated. You seem to be sending an array with the project.
Thank you so much. This helped me.
I had the situation that (valid) PUT test was failing, as was the (valid) DELETE test.
Taking a look at the test, I noticed that within the PUT test, a POST request happens before. So when I wrote according test and did some console.logging, I found out that the MongoDB ObjectId()s were causing the problem that I did not actually find the issue that had to be updated or deleted. using .toString() was the solution then.