Add Life Goes On

Fixes #202

lib/magic/cards/life_goes_on.rb

@@ -0,0 +1,16 @@
+module Magic
+  module Cards
+    class LifeGoesOn < Instant
+      card_name "Life Goes On"
+      cost "{G}"
+
+      def resolve!
+        creature_died = current_turn.events.count { |event| event.is_a?(Events::CreatureDied) } > 0
+        life_gain = 4
+        life_gain += 4 if creature_died
+
+        trigger_effect(:gain_life, life: life_gain)
+      end
+    end
+  end
+end

spec/cards/life_goes_on_spec.rb

@@ -0,0 +1,35 @@
+require "spec_helper"
+
+RSpec.describe Magic::Cards::LifeGoesOn do
+  include_context "two player game"
+  let(:life_goes_on) { Card("Life Goes On") }
+  context "when no creature died" do
+    it "player gains 4 life" do
+      p1.add_mana(green: 1)
+      p1.cast(card: life_goes_on) do
+        _1.pay_mana(green: 1)
+      end
+
+      game.tick!
+      expect(p1.life).to eq(24)
+    end
+  end
+
+  context "when a creature died" do
+    let(:creature) { ResolvePermanent("Wood Elves") }
+
+    before do
+      creature.sacrifice!
+    end
+
+    it "player gains 8 life" do
+      p1.add_mana(green: 1)
+      p1.cast(card: life_goes_on) do
+        _1.pay_mana(green: 1)
+      end
+
+      game.tick!
+      expect(p1.life).to eq(28)
+    end
+  end
+end