💄 improve assertion error messages in DfsMazeSolverTest

[twentylemon]

What

Replacing assertions like assertTrue(solution.equals(x) || solution.equals(y)) with assertions that give more information when they fail. AssertJ's isIn would be ideal, or at least recreating that type of assertion.

Why

Tests are substantially more useful when they give information on why they failed. Assertions like assertTrue are black holes. The message you get for failures is expected false to be true. The isIn assertion gives a message like expected blah to be equal to one of x, y, z, where it toStrings each of the values. It tells you exactly the expectation, and what you actually gave it.

Where

DfsMazeSolverTest

How

Given it's unlikely to onboard AssertJ, simply adding a custom message to the existing assertions is probably sufficient.

[jameshughes89]

AssertJ may make an entrance next year since, if simple unit testing is done in cs101, then adding more to the testing at this stage seems more doable.