# Reflecting on test-driven attempt at solving an old interview problem.

04 Nov 2019

In earlier blog posts, I documented my process for building a test-driven solution to an old interview problem. The test files and matching production code files are shown below.

Before attempting to solve this problem, I had been really struggling to learn TDD for a while. I wasn't sure if I'd get very far trying to test-drive the following code but was actually pleasantly surprised. Something clicked with TDD a bit more. I could see how it can help drive a design.

The solution below is incomplete. I was able to test-drive all of the individual pieces that make up the solution. However, I am missing some object-oriented design skills which meant that I wasn't sure how to make the pieces all work together as collaborating objects without calling them in a procedural way.

To get better, it could help to learn more about design patterns to get more exposure to object-oriented style solutions. So close to being able to do this all properly though, just got to keep at it!

## spec/tetris_game_spec.rb

``````
require_relative '../lib/tetris_game.rb'
require_relative '../lib/block.rb'

describe 'TetrisGame should:' do

it '- Have a block capacity.' do
tetris = TetrisGame.new 1
expect(tetris.block_capacity).to eql(1)
end
it '- Not have a block capacity less than 1.' do
tetris = TetrisGame.new -1
expect(tetris.block_capacity).to eql(nil)
end
it '- Have a starting tile' do
tetris = TetrisGame.new
expect(tetris.starting_tile).to eql(1)
end
it '- Confirm room for more blocks.' do
[3, 6, 12, 34, 3029, 199].each do |num|
tetris = TetrisGame.new 3500
expect(tetris.is_there_room_for_this(Block.new num)).to eql(true)
end
end
it '- Deny room for more blocks.' do
[33, 24, 43, 92, 103].each do |num|
tetris = TetrisGame.new 1
expect(tetris.is_there_room_for_this(Block.new num)).to eql(false)
end
end
it '- Reduce block capacity when a block is added.' do
tetris = TetrisGame.new 1
expect(tetris.block_capacity).to eql(0)
end
it '- Add blocks unless capacity is reached.' do
tetris = TetrisGame.new 20
block_sizes = [1, 2, 5, 15, 200, 30, 9, 19, 2, 1]

block_sizes.each do |num|
end
expect(tetris.block_capacity).to eql(0)
end
it '- Show blocks added to the game.' do
tetris = TetrisGame.new 20
3.times { tetris.add_block(Block.new 1) }
expect(tetris.blocks.length).to eql(3)
expect(tetris.blocks[0].shape).to eql("Block")
end
it '- Show leftover blocks that wont fit.' do
tetris = TetrisGame.new 20
5.times { tetris.add_block(Block.new 10) }
expect(tetris.leftover_blocks.length).to eql(3)
end
it '- Show position, size and shape of each block' do
tetris = TetrisGame.new 10
expect(tetris.describe(tetris.blocks)).to eql(['1-2: Block 2','2-5: Block 4'])
end
it '- Change block size 3 to "golden"' do
tetris = TetrisGame.new 10
expect(tetris.describe(tetris.blocks)).to eql(['1-3: Block golden', '3-4: Block 2'])
end
end
```
```

## spec/block_spec.rb

``````
tetris_game_spec.rb                                           74,1           Bot
require_relative '../lib/block.rb'

describe 'Block should:' do
it '- Be a specific size.' do
[1,2,3,5,10,200,36,42,19].each do |num|
block = Block.new num
expect(block.size).to eql(num)
end
end
it '- Not be smaller than a size 1.' do
block = Block.new -2
expect(block.size).to eql(nil)
end
it '- Have a shape.' do
block = Block.new
expect(block.shape).to eql('Block')
end
it '- Display information about itself.' do
block = Block.new 1
end

end
```
```

## lib/tetris_game.rb

``````
class TetrisGame
attr_reader :block_capacity, :blocks, :leftover_blocks, :starting_tile

def initialize(block_capacity = 0, starting_tile = 1)
@starting_tile = starting_tile
@blocks = []
@leftover_blocks = []
if block_capacity > 0
@block_capacity = block_capacity
end
end

def is_there_room_for_this(block)
block.size <= @block_capacity
end

if is_there_room_for_this(block)
@block_capacity = @block_capacity - block.size
@blocks << block
else
@leftover_blocks << block
end
end

def describe(blocks)
blocks = []
@blocks.each do |block|
blocks << "#{@starting_tile}-#{@starting_tile + block.size - 1}: #{block.shape} #{block_size_formatter(block.size)}"
@starting_tile += block.size - 1
end
blocks
end

def block_size_formatter(size)
if size == 3
"golden"
else
size
end
end

end
```
```

## lib/block.rb

``````
class Block

def initialize(size = 0, shape = 'Block')
if size > 0
@size = size
end
@shape = shape
end