add snake game

pkg/snake/snake_test.go

@@ -0,0 +1,62 @@
+package snake
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSnake(t *testing.T) {
+	scenarios := []struct {
+		state         State
+		expectedState State
+		expectedAlive bool
+	}{
+		{
+			state: State{
+				snakePositions: []Position{{x: 5, y: 5}},
+				direction:      Right,
+				foodPosition:   Position{x: 9, y: 9},
+			},
+			expectedState: State{
+				snakePositions: []Position{{x: 6, y: 5}},
+				direction:      Right,
+				foodPosition:   Position{x: 9, y: 9},
+			},
+			expectedAlive: true,
+		},
+		{
+			state: State{
+				snakePositions: []Position{{x: 5, y: 5}, {x: 4, y: 5}, {x: 4, y: 4}, {x: 5, y: 4}},
+				direction:      Up,
+				foodPosition:   Position{x: 9, y: 9},
+			},
+			expectedState: State{},
+			expectedAlive: false,
+		},
+		{
+			state: State{
+				snakePositions: []Position{{x: 5, y: 5}},
+				direction:      Right,
+				foodPosition:   Position{x: 6, y: 5},
+			},
+			expectedState: State{
+				snakePositions: []Position{{x: 6, y: 5}, {x: 5, y: 5}},
+				direction:      Right,
+				foodPosition:   Position{x: 8, y: 8},
+			},
+			expectedAlive: true,
+		},
+	}
+
+	for _, scenario := range scenarios {
+		game := NewGame(10, 10, nil)
+		game.state = scenario.state
+		game.randIntFn = func(int) int { return 8 }
+		alive := game.tick()
+		assert.Equal(t, scenario.expectedAlive, alive)
+		if scenario.expectedAlive {
+			assert.EqualValues(t, scenario.expectedState, game.state)
+		}
+	}
+}