Graham McIntire
4c1013cdbd
Cover the pure-math invariants of the ITU-R P.526-16 diffraction helpers, the haversine metric on Geo, and the Magnus / dry-adiabat helpers in the skew-T renderer. 29 properties, one invariant each.
119 lines
3.9 KiB
Elixir
119 lines
3.9 KiB
Elixir
defmodule MicrowavepropWeb.SkewTPropertyTest do
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@moduledoc """
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StreamData property tests for `MicrowavepropWeb.SkewT`'s atmospheric
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math helpers.
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Invariants covered:
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* Magnus saturation vapor pressure is positive and strictly
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monotonic in temperature.
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* `temperature_from_mixing_ratio/2` is the inverse of the
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ws = 622·es / (p − es) forward relation.
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* Along a dry adiabat, temperature decreases monotonically as
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pressure falls (lift a parcel → it cools).
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* At the 1000 mb reference pressure, dry-adiabat T equals θ − 273.15
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(definition of potential temperature).
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* `project/3` reproduces the chart corners and preserves pressure
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ordering on the y-axis.
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"""
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use ExUnit.Case, async: true
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use ExUnitProperties
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alias MicrowavepropWeb.SkewT
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describe "saturation_vapor_pressure/1" do
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property "is strictly positive across the troposphere" do
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check all(t_c <- float(min: -80.0, max: 50.0)) do
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assert SkewT.saturation_vapor_pressure(t_c) > 0
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end
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end
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property "is strictly monotonic in temperature" do
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check all(
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t_c <- float(min: -80.0, max: 50.0),
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delta <- float(min: 0.001, max: 10.0)
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) do
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lo = SkewT.saturation_vapor_pressure(t_c)
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hi = SkewT.saturation_vapor_pressure(t_c + delta)
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assert hi > lo
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end
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end
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end
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describe "temperature_from_mixing_ratio/2" do
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property "round-trips T → ws → T for realistic (T, p) pairs" do
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check all(
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t_c <- float(min: -30.0, max: 35.0),
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p_mb <- float(min: 300.0, max: 1050.0)
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) do
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es = SkewT.saturation_vapor_pressure(t_c)
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# Only test where ws is well-defined (p > es).
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if p_mb > es + 1.0 do
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ws_g_kg = 622.0 * es / (p_mb - es)
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recovered = SkewT.temperature_from_mixing_ratio(ws_g_kg, p_mb)
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assert_in_delta recovered, t_c, 0.01
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end
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end
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end
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end
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describe "dry_adiabat_temperature/2" do
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property "equals θ − 273.15 at the 1000 mb reference pressure" do
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check all(theta_k <- float(min: 200.0, max: 400.0)) do
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t_c = SkewT.dry_adiabat_temperature(theta_k, 1000.0)
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assert_in_delta t_c, theta_k - 273.15, 1.0e-6
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end
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end
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property "temperature decreases as pressure decreases along an adiabat" do
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check all(
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theta_k <- float(min: 250.0, max: 360.0),
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p_hi <- float(min: 500.0, max: 1050.0),
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drop <- float(min: 10.0, max: 400.0)
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) do
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p_lo = p_hi - drop
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if p_lo > 50.0 do
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t_hi = SkewT.dry_adiabat_temperature(theta_k, p_hi)
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t_lo = SkewT.dry_adiabat_temperature(theta_k, p_lo)
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assert t_hi > t_lo
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end
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end
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end
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end
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describe "project/3" do
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setup do
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%{chart: SkewT.chart_config([])}
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end
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property "projects p_bot to the plot bottom and p_top to the plot top",
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%{chart: chart} do
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check all(t_c <- float(min: chart.t_min, max: chart.t_max)) do
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{_x_bot, y_bot} = SkewT.project(t_c, chart.p_bot, chart)
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{_x_top, y_top} = SkewT.project(t_c, chart.p_top, chart)
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# SVG y grows downward: the bottom of the chart has a larger y.
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assert y_bot > y_top
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assert_in_delta y_bot, chart.padding_top + chart.plot_height, 1.0e-6
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assert_in_delta y_top, chart.padding_top, 1.0e-6
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end
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end
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property "pressure ordering is inverted on the y-axis (higher p → larger y)",
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%{chart: chart} do
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check all(
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p_hi <- float(min: 200.0, max: 1050.0),
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p_lo <- float(min: 100.0, max: 1000.0),
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t_c <- float(min: -20.0, max: 20.0)
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) do
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if p_hi > p_lo + 1.0 do
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{_x1, y_hi} = SkewT.project(t_c, p_hi, chart)
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{_x2, y_lo} = SkewT.project(t_c, p_lo, chart)
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assert y_hi > y_lo
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end
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end
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end
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end
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end
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