This is the implementation for the second requirement.
We can split this requirement into the following tests:
- When a disc is inserted into an empty column, its position is 0
- When a second disc is inserted into the same column, its position is 1
- When a disc is inserted into the board, the total number of discs increases
- When a disc is put outside the boundaries, a Runtime Exception is thrown
- When a disc is inserted into a column and there's no room available for it, then a Runtime Exception is thrown
Also, these other ...