This test is duplicating the code inside the `id` getter, documenting "how" is the id increated, but not capturing "why" it has to be created this way. (What is the contract of the `id` property that we are relying on.)

A better way would be to add three tests:
 1. Two Change instances with the same `modelName` and `modelId` have the same `id`, regardless of the value of other properties (they should differ in this test).
 2. Instances with different `modelId` values have different hash, regardless of the value of other properties (they should be same in this test).
 3. Instances with different `modelName` values have different hash, regardless of the value of other properties (they should be same in this test).