Java Event Driven Development problem with square bracket in assertEquals

I do classic Event Driven Development Testing.

// given

// when

// then
then(response.getStatus()).isEqualTo(HttpStatus.OK.value());

then(response.getContentAsString()).isEqualTo(
      jsonRequestProduct.write(List.of(newProduct)).getJson());

And I will get response from second line of code.

org.opentest4j.AssertionFailedError: Expecting: ... but was not.

Expected :"[{"id":1,"description":"iPhone 33","price":599.99}]"
Actual   :"{"id":1,"description":"iPhone 33","price":599.99}"

Question: How do i get rid of "[ ]" so my test will pass?

Thanks for advice.

UPDATE:

Required type: List<xxx.demo.model.Product>

Provided: Product

This is how my controller looks like.

    @PutMapping("/update")
    public ResponseEntity<Product> updateProduct(@RequestBody Product product) {
         return ResponseEntity.ok(productServiceImpl.updateProduct(product));
    }