57 lines
1.8 KiB
Ruby
57 lines
1.8 KiB
Ruby
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# frozen_string_literal: true
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require_relative "helper"
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require "rack/test"
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require "versions/v2"
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# Contract tests for the V2 API:
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# - reciprocal: rate(A,B) * rate(B,A) == 1 (rounded)
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# - cross-rate transitivity: rate(A,B) * rate(B,C) * rate(C,A) == 1 (rounded)
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# - pegged-base anchor: pegged base requests resolve to the peg, not provider noise
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#
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# The reciprocal and transitivity tests fail on `main` for non-USD bases — they're the
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# defining checks of the fix. The pegged-base test passes today; it's a regression guard.
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describe "V2 reciprocal consistency" do
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include Rack::Test::Methods
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let(:app) { Versions::V2.freeze }
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def rate_for(base:, quote:)
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get("/rates?base=#{base}"es=#{quote}")
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raise "request failed: #{last_response.status}" unless last_response.ok?
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row = Oj.load(last_response.body).find { |r| r["quote"] == quote }
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raise "no rate returned for #{base}->#{quote}" unless row
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row["rate"]
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end
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it "rate(A,B) * rate(B,A) rounds to 1.0 for USD/GBP" do
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forward = rate_for(base: "USD", quote: "GBP")
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backward = rate_for(base: "GBP", quote: "USD")
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_((forward * backward).round(4)).must_equal(1.0)
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end
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it "rate(A,B) * rate(B,A) rounds to 1.0 for USD/CAD" do
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forward = rate_for(base: "USD", quote: "CAD")
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backward = rate_for(base: "CAD", quote: "USD")
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_((forward * backward).round(4)).must_equal(1.0)
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end
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it "transitivity holds across USD, EUR, GBP" do
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a_b = rate_for(base: "USD", quote: "EUR")
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b_c = rate_for(base: "EUR", quote: "GBP")
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c_a = rate_for(base: "GBP", quote: "USD")
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_((a_b * b_c * c_a).round(4)).must_equal(1.0)
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end
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it "pegged base resolves to the peg, not provider noise" do
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rate = rate_for(base: "AED", quote: "USD")
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_(rate).must_equal((1.0 / 3.6725).round(5))
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end
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end
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