Help users understand more clearly when the store is misconfigured

lib/rack/attack.rb

@@ -2,6 +2,9 @@ require 'rack'
 require 'forwardable'
 
 class Rack::Attack
+  class MisconfiguredStoreError < StandardError; end
+  class MissingStoreError < StandardError; end
+
   autoload :Cache,           'rack/attack/cache'
   autoload :PathNormalizer,  'rack/attack/path_normalizer'
   autoload :Check,           'rack/attack/check'

lib/rack/attack/cache.rb

@@ -46,15 +46,20 @@ module Rack
       end
 
       def do_count(key, expires_in)
-        result = store.increment(key, 1, :expires_in => expires_in)
+        if store.nil?
+          raise Rack::Attack::MissingStoreError
+        elsif !store.respond_to?(:increment)
+          raise Rack::Attack::MisconfiguredStoreError, "Store needs to respond to #increment"
+        else
+          result = store.increment(key, 1, :expires_in => expires_in)
 
-        # NB: Some stores return nil when incrementing uninitialized values
-        if result.nil?
-          store.write(key, 1, :expires_in => expires_in)
+          # NB: Some stores return nil when incrementing uninitialized values
+          if result.nil?
+            store.write(key, 1, :expires_in => expires_in)
+          end
+          result || 1
         end
-        result || 1
       end
-
     end
   end
 end

spec/rack_attack_store_config_spec.rb

@@ -0,0 +1,20 @@
+require_relative 'spec_helper'
+
+describe 'Store configuration' do
+  it "gives clear error when store it's not configured if it's needed" do
+    Rack::Attack.throttle('ip/sec', limit: 1, period: 60) { |req| req.ip }
+
+    assert_raises(Rack::Attack::MissingStoreError) do
+      get '/'
+    end
+  end
+
+  it "gives clear error when store isn't configured properly" do
+    Rack::Attack.cache.store = Object.new
+    Rack::Attack.throttle('ip/sec', limit: 1, period: 60) { |req| req.ip }
+
+    assert_raises(Rack::Attack::MisconfiguredStoreError) do
+      get '/'
+    end
+  end
+end

spec/spec_helper.rb

@@ -19,7 +19,10 @@ class MiniTest::Spec
 
   include Rack::Test::Methods
 
-  after { Rack::Attack.clear! }
+  after do
+    Rack::Attack.clear!
+    Rack::Attack.instance_variable_set(:@cache, nil)
+  end
 
   def app
     Rack::Builder.new {