DEV-765 add some additional tests (#65)

Adds additional test coverage. Re-uses standard test cases where possible and added a few additional cases specific to some modes.

cases_test.go

@@ -0,0 +1,41 @@
+package rules
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type gameTestCase struct {
+	name          string
+	prevState     *BoardState
+	moves         []SnakeMove
+	expectedError error
+	expectedState *BoardState
+}
+
+func (gc *gameTestCase) clone() *gameTestCase {
+	return &gameTestCase{
+		name:          gc.name,
+		expectedError: gc.expectedError,
+		moves:         append([]SnakeMove{}, gc.moves...),
+		prevState:     gc.prevState.Clone(),
+		expectedState: gc.expectedState.Clone(),
+	}
+}
+
+// requireValidNextState requires that the ruleset produces a valid next state
+func (gc *gameTestCase) requireValidNextState(t *testing.T, r Ruleset) {
+	t.Run(gc.name, func(t *testing.T) {
+		prev := gc.prevState.Clone() // clone to protect against mutation (so we can ru-use test cases)
+		nextState, err := r.CreateNextBoardState(prev, gc.moves)
+		require.Equal(t, gc.expectedError, err)
+		if gc.expectedState != nil {
+			require.Equal(t, gc.expectedState.Width, nextState.Width)
+			require.Equal(t, gc.expectedState.Height, nextState.Height)
+			require.Equal(t, gc.expectedState.Food, nextState.Food)
+			require.Equal(t, gc.expectedState.Snakes, nextState.Snakes)
+			require.Equal(t, gc.expectedState.Hazards, nextState.Hazards)
+		}
+	})
+}