A method of testing the coking qualities of sample quantities of coal in a test container and the structure of the test container are disclosed. A test container which is ideally reusable is adapted to receive one or more samples of coal to be tested and then the test container is inserted into a coking oven along with additional, conventional coal during a conventional coking operation. Following the completion or substantial completion of the coking operation, the test container is recovered and from the conventional converted coke and the sample(s) of coke are removed from the container for testing and evaluation. The container is recharged with one or more additional samples of coke and reused in another conventional coking operation.