DEV-1556-sinkholes-map (#96)

* initial map implementation

* added support for larger/smaller boards

* basic unit test

maps/sinkholes_test.go

@@ -0,0 +1,57 @@
+package maps_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/BattlesnakeOfficial/rules"
+	"github.com/BattlesnakeOfficial/rules/maps"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSinkholesMap(t *testing.T) {
+
+	tests := []struct {
+		boardSize               int
+		expectedHazards         int
+		expectedHazardsInCenter int
+	}{
+		{7, 27, 3},
+		{11, 149, 5},
+		{19, 431, 7},
+	}
+
+	for _, tc := range tests {
+
+		t.Run(fmt.Sprintf("%dx%d", tc.boardSize, tc.boardSize), func(t *testing.T) {
+			m := maps.SinkholesMap{}
+			state := rules.NewBoardState(tc.boardSize, tc.boardSize)
+			settings := rules.Settings{}
+
+			// ensure the ring of hazards is added to the board at setup
+			editor := maps.NewBoardStateEditor(state)
+			require.Empty(t, state.Hazards)
+			err := m.SetupBoard(state, settings, editor)
+			require.NoError(t, err)
+			require.Empty(t, state.Hazards)
+
+			totalTurns := 100
+			for i := 0; i < totalTurns; i++ {
+				state.Turn = i
+				err = m.UpdateBoard(state, settings, editor)
+				require.NoError(t, err)
+			}
+			require.NotEmpty(t, state.Hazards)
+			require.Len(t, state.Hazards, tc.expectedHazards)
+
+			centerPoint := rules.Point{X: tc.boardSize / 2, Y: tc.boardSize / 2}
+			numCenterHazards := 0
+			for _, p := range state.Hazards {
+				if p == centerPoint {
+					numCenterHazards += 1
+				}
+			}
+			require.Equal(t, numCenterHazards, tc.expectedHazardsInCenter)
+		})
+	}
+}