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36a43f3a35
Pure-Ruby projection engine for a single plan. Models in real (today's-money) terms: portfolio grows at the real return, spending and pension incomes are held in today's money, so no inflation parameter is needed and output is fully deterministic. v2 swaps in a Sidekiq Monte Carlo behind the same call interface. POROs (app/models/retirement/): - Fire::Forecast — annual stepper. Accumulate (×(1+r)+savings) to retire_age, then draw down max(target − net pension income, 0) with lump payouts as portfolio deltas. Computes the glide series, money-lasts-to age, terminal value, Coast FIRE age (bisection on the minimum survivable portfolio at retirement), feasibility, warnings. - Fire::Payout — normalises a PensionSource to gross annual income + one-time lump per age, across the four payout shapes. - Fire::Adjustment — age-bounded signed change to the spending target. - Fire::CohortAccess — min access age (UK NMPA 55→57 from 2028, US 59.5/62, DE 63/55). - Tax::StaticRate (+ initializer) — v1 fraction-kept by treatment; de_renten falls with the cohort year. Boot-validated against the PensionSource enum. Wiring: Goal::Retirement gains retirement_params store_accessor (birth_year, retire_age, real_return_pct, monthly_savings, target_spend, terminal_age), bucket_value, payouts, forecast_inputs, memoised #forecast (nil until birth_year set), freedom_date, coast_fire_date. Family#retirement_spending_baseline anchors the default target on the median monthly expense (the precise trailing-12m 10%-trimmed mean + its label ship with PR4's "Why this target?" card). Tests: 28 — exact zero-return stepper checks (accumulation + depletion with shortfall), pension-covered no-drawdown, tax widening the drawdown, adjustment lowering the target, Coast extremes, infeasible warnings, plus tax/payout/cohort units and the model wiring. No new gems.
109 lines
3.8 KiB
Ruby
109 lines
3.8 KiB
Ruby
require "test_helper"
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class Retirement::Fire::ForecastTest < ActiveSupport::TestCase
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Forecast = Retirement::Fire::Forecast
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Inputs = Retirement::Fire::Inputs
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Payout = Retirement::Fire::Payout
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Adjustment = Retirement::Fire::Adjustment
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def inputs(**over)
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defaults = {
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current_age: 40, retire_age: 65, terminal_age: 95, real_return: 0.05,
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annual_savings: 0, annual_target_spend: 24_000, starting_portfolio: 0,
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retire_year: 2050, payouts: [], target_adjustments: []
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}
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Inputs.new(**defaults.merge(over))
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end
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def payout(**over)
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Payout.new(**{ kind: "state", shape: "monthly_for_life", tax_treatment: "custom_post_tax", start_age: 65, monthly_amount: 0 }.merge(over))
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end
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test "accumulation is deterministic (zero return-free check)" do
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result = Forecast.new(inputs(
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current_age: 64, retire_age: 65, terminal_age: 66,
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real_return: 0.10, annual_savings: 1000, starting_portfolio: 1000,
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annual_target_spend: 0
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)).call
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assert_equal [ [ 64, 1000 ], [ 65, 2100 ], [ 66, 2310 ] ], result.glide
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assert result.feasible
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assert_equal 2310, result.terminal_value
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end
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test "drawdown depletion is exact and flags shortfall" do
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result = Forecast.new(inputs(
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current_age: 65, retire_age: 65, terminal_age: 67,
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real_return: 0.0, starting_portfolio: 100, annual_target_spend: 60
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)).call
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assert_equal [ [ 65, 100 ], [ 66, 40 ], [ 67, 0 ] ], result.glide
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assert_not result.feasible
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assert_equal 66, result.money_lasts_to_age
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assert_equal 0, result.terminal_value
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last = result.income_by_year.last
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assert_equal 40, last[:drawdown]
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assert_equal 20, last[:shortfall]
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assert_includes result.warnings, "depletes_before_terminal"
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end
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test "a pension that fully covers spend means no drawdown" do
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result = Forecast.new(inputs(
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retire_age: 65, starting_portfolio: 0, annual_target_spend: 24_000,
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payouts: [ payout(kind: "state", start_age: 65, monthly_amount: 2000) ]
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)).call
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assert result.feasible
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assert result.lasts_past_terminal?
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first_draw = result.income_by_year.first
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assert_equal 24_000, first_draw[:state]
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assert_equal 0, first_draw[:drawdown]
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end
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test "tax reduces net pension income and widens the drawdown" do
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result = Forecast.new(inputs(
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retire_age: 65, starting_portfolio: 5_000_000, annual_target_spend: 24_000,
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payouts: [ payout(kind: "workplace", tax_treatment: "de_bav", start_age: 65, monthly_amount: 2000) ]
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)).call
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row = result.income_by_year.first
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assert_equal 17_760, row[:workplace] # 24,000 gross * 0.74
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assert_equal 6_240, row[:drawdown] # 24,000 - 17,760
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end
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test "a negative adjustment lowers the target spend from its age" do
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result = Forecast.new(inputs(
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retire_age: 65, starting_portfolio: 5_000_000, annual_target_spend: 24_000,
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target_adjustments: [ Adjustment.new(from_age: 65, to_age: nil, annual_amount: -12_000) ]
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)).call
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assert_equal 12_000, result.income_by_year.first[:drawdown]
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end
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test "coast_age is current_age when already over-funded" do
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result = Forecast.new(inputs(
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starting_portfolio: 10_000_000, annual_savings: 0, annual_target_spend: 24_000
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)).call
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assert_equal 40, result.coast_age
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assert result.feasible
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end
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test "infeasible plan has no coast age and warns" do
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result = Forecast.new(inputs(
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starting_portfolio: 0, annual_savings: 0, annual_target_spend: 100_000
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)).call
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assert_nil result.coast_age
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assert_not result.feasible
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assert_includes result.warnings, "infeasible_no_coast"
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end
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test "glide spans current_age to terminal_age inclusive" do
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result = Forecast.new(inputs(current_age: 30, terminal_age: 95)).call
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assert_equal 30, result.glide.first.first
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assert_equal 95, result.glide.last.first
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assert_equal 66, result.glide.length
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end
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end
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