Add srem? for redis-rb compatibility

lib/mock_redis/set_methods.rb

@@ -137,6 +137,11 @@ def srem(key, members)
       end
     end
 
+    def srem?(key, members)
+      res = srem(key, members)
+      res.is_a?(Numeric) ? res > 0 : res
+    end
+
     def sscan(key, cursor, opts = {})
       common_scan(smembers(key), cursor, opts)
     end

spec/commands/srem_spec.rb

@@ -41,5 +41,20 @@
     expect(@redises.srem(@key, [1, 2])).to eq(2)
   end
 
+  context 'srem?' do
+    it 'returns true if member is in the set' do
+      expect(@redises.srem?(@key, 'bert')).to eq(true)
+    end
+
+    it 'returns false if member is not in the set' do
+      expect(@redises.srem?(@key, 'cookiemonster')).to eq(false)
+    end
+
+    it 'removes member from the set' do
+      @redises.srem?(@key, 'ernie')
+      expect(@redises.smembers(@key)).to eq(['bert'])
+    end
+  end
+
   it_should_behave_like 'a set-only command'
 end