Add a helper for exercising some Stripe interactions

PaymentServer.cabal

@@ -73,9 +73,12 @@ test-suite PaymentServer-tests
   main-is:             Spec.hs
   other-modules:       Persistence
                      , Metrics
+                     , FakeStripe
   build-depends:       base
                      , bytestring
                      , text
+                     , raw-strings-qq
+                     , time
                      , tasty
                      , tasty-hunit
                      , directory
@@ -84,6 +87,8 @@ test-suite PaymentServer-tests
                      , http-types
                      , wai
                      , wai-extra
+                     , warp
+                     , http-types
                      , servant-server
                      , prometheus-client
                      , stripe-core

test/FakeStripe.hs

+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module FakeStripe
+  ( withFakeStripe
+  , chargeOkay
+  ) where
+
+import Text.RawString.QQ
+
+import Data.ByteString.Lazy
+   ( ByteString
+   )
+
+import Data.Time.Clock
+  ( UTCTime(UTCTime)
+  , secondsToDiffTime
+  )
+
+import Data.Time.Calendar
+  ( Day(ModifiedJulianDay)
+  )
+
+import Network.HTTP.Types
+  ( status200
+  )
+
+import Network.Wai
+  ( Application
+  , responseLBS
+  )
+
+import Network.Wai.Handler.Warp
+  ( testWithApplication
+  )
+
+import Web.Stripe.Client
+  ( StripeConfig(StripeConfig)
+  , StripeKey(StripeKey)
+  , Protocol(HTTP)
+  , Endpoint(Endpoint)
+  )
+
+aCharge :: ByteString
+aCharge = [r|
+{
+  "id": "ch_1Fwa4NBHXBAMm9bPFRPo6UBt",
+  "object": "charge",
+  "amount": 100,
+  "amount_captured": 0,
+  "amount_refunded": 0,
+  "application": null,
+  "application_fee": null,
+  "application_fee_amount": null,
+  "balance_transaction": "txn_1FrU7mBHXBAMm9bP9WvFFzRG",
+  "billing_details": {
+    "address": {
+      "city": "",
+      "country": "US",
+      "line1": "",
+      "line2": "",
+      "postal_code": "",
+      "state": "Select State"
+    },
+    "email": null,
+    "name": "",
+    "phone": null
+  },
+  "calculated_statement_descriptor": null,
+  "captured": false,
+  "created": 1577996099,
+  "currency": "usd",
+  "customer": null,
+  "description": null,
+  "disputed": false,
+  "failure_code": "card_declined",
+  "failure_message": "Your card was declined.",
+  "fraud_details": {
+    "stripe_report": "fraudulent"
+  },
+  "invoice": null,
+  "livemode": false,
+  "metadata": {
+    "Voucher": "EQwTqWXIjKF5MWMZmDYKJvbtiaVBlDecmk__bytPlK_l"
+  },
+  "on_behalf_of": null,
+  "order": null,
+  "outcome": {
+    "network_status": "not_sent_to_network",
+    "reason": "merchant_blacklist",
+    "risk_level": "highest",
+    "risk_score": 90,
+    "seller_message": "Stripe blocked this payment.",
+    "type": "blocked"
+  },
+  "paid": false,
+  "payment_intent": null,
+  "payment_method": "card_1Fwa4MBHXBAMm9bPyw1fke3O",
+  "payment_method_details": {
+    "card": {
+      "brand": "visa",
+      "checks": {
+        "address_line1_check": null,
+        "address_postal_code_check": null,
+        "cvc_check": "unavailable"
+      },
+      "country": "US",
+      "exp_month": 11,
+      "exp_year": 2022,
+      "fingerprint": "5COYv5EoHE9ZE82J",
+      "funding": "credit",
+      "installments": null,
+      "last4": "0019",
+      "network": "visa",
+      "three_d_secure": null,
+      "wallet": null
+    },
+    "type": "card"
+  },
+  "receipt_email": null,
+  "receipt_number": null,
+  "receipt_url": null,
+  "refunded": false,
+  "refunds": {
+    "object": "list",
+    "data": [],
+    "has_more": false,
+    "url": "/v1/charges/ch_1Fwa4NBHXBAMm9bPFRPo6UBt/refunds"
+  },
+  "review": null,
+  "shipping": null,
+  "source_transfer": null,
+  "statement_descriptor": null,
+  "statement_descriptor_suffix": null,
+  "status": "failed",
+  "transfer_data": null,
+  "transfer_group": null
+}
+|]
+
+-- Accept a charge creation and respond in the affirmative.
+chargeOkay :: Application
+chargeOkay req respond =
+  respond . responseLBS status200 [] $ aCharge
+
+-- Pass a Stripe-flavored configuration for a running Wai application to a
+-- function and evaluate the resulting IO action.
+withFakeStripe :: IO Application -> (StripeConfig -> IO a) -> IO a
+withFakeStripe app f =
+  testWithApplication app $ f . makeConfig
+  where
+    makeConfig = StripeConfig stripeKey . Just . Endpoint "127.0.0.1" HTTP
+    stripeKey = StripeKey "pk_test_aaaaaaaaaaaaaaaaaaaaaa"