Add solo gameplay ruleset.

solo.go

@@ -0,0 +1,14 @@
+package rules
+
+type SoloRuleset struct {
+	StandardRuleset
+}
+
+func (r *SoloRuleset) IsGameOver(b *BoardState) (bool, error) {
+	for i := 0; i < len(b.Snakes); i++ {
+		if b.Snakes[i].EliminatedCause == NotEliminated {
+			return false, nil
+		}
+	}
+	return true, nil
+}

solo_test.go

@@ -0,0 +1,48 @@
+package rules
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSoloCreateNextBoardStateSanity(t *testing.T) {
+	boardState := &BoardState{}
+	r := SoloRuleset{}
+	_, err := r.CreateNextBoardState(boardState, []SnakeMove{})
+	require.NoError(t, err)
+}
+
+func TestSoloIsGameOver(t *testing.T) {
+	tests := []struct {
+		Snakes   []Snake
+		Expected bool
+	}{
+		{[]Snake{}, true},
+		{[]Snake{{}}, false},
+		{[]Snake{{}, {}, {}}, false},
+		{[]Snake{{EliminatedCause: EliminatedByOutOfBounds}}, true},
+		{
+			[]Snake{
+				{EliminatedCause: EliminatedByOutOfBounds},
+				{EliminatedCause: EliminatedByOutOfBounds},
+				{EliminatedCause: EliminatedByOutOfBounds},
+			},
+			true,
+		},
+	}
+
+	r := SoloRuleset{}
+	for _, test := range tests {
+		b := &BoardState{
+			Height: 11,
+			Width:  11,
+			Snakes: test.Snakes,
+			Food:   []Point{},
+		}
+
+		actual, err := r.IsGameOver(b)
+		require.NoError(t, err)
+		require.Equal(t, test.Expected, actual)
+	}
+}