implement conceding

game/game.go

@@ -163,6 +163,21 @@ func (g *Game) Shoot(id player.ID, self bool) error {
 	return nil
 }
 
+// Concede sets the player with the given ID to zero health. The returned
+// Boolean indicates whether the game has ended. (It will be false if id does
+// not correspond to either player.)
+func (g *Game) Concede(id player.ID) bool {
+	switch id {
+	case g.players[0].id:
+		g.players[0].hp = 0
+	case g.players[1].id:
+		g.players[1].hp = 0
+	default:
+		return false
+	}
+	return true
+}
+
 // DTO returns the current game state as viewed by the given player.
 func (g *Game) DTO(id player.ID) serve.Game {
 	return serve.Game{

game/game_test.go

@@ -405,6 +405,42 @@ func TestGameShoot(t *testing.T) {
 	}
 }
 
+func TestConcede(t *testing.T) {
+	dealer, chall := player.ID{1}, player.ID{2}
+	cases := []struct {
+		name   string
+		p      player.ID
+		winner player.ID
+	}{
+		{
+			name:   "dealer",
+			p:      dealer,
+			winner: chall,
+		},
+		{
+			name:   "challenger",
+			p:      chall,
+			winner: dealer,
+		},
+		{
+			name:   "neither",
+			p:      player.ID{3},
+			winner: player.ID{},
+		},
+	}
+	for _, c := range cases {
+		c := c
+		t.Run(c.name, func(t *testing.T) {
+			t.Parallel()
+			g := New(dealer, chall)
+			g.Concede(c.p)
+			if got := g.Winner(); deref(got).id != c.winner {
+				t.Errorf("wrong winner: %#v doesn't have id %#v", got, c.winner)
+			}
+		})
+	}
+}
+
 func TestGameShellCounts(t *testing.T) {
 	cases := []struct {
 		name   string