Maybe/test/models/trend_test.rb

require "test_helper"

class TrendTest < ActiveSupport::TestCase
  test "handles money trend" do
    trend = Trend.new(current: Money.new(100), previous: Money.new(50))
    assert_equal "up", trend.direction
    assert_equal Money.new(50), trend.value
    assert_equal 100.0, trend.percent
  end

  test "up" do
    trend = Trend.new(current: 100, previous: 50)
    assert_equal "up", trend.direction
    assert_equal "var(--color-success)", trend.color
  end

  test "down" do
    trend = Trend.new(current: 50, previous: 100)
    assert_equal "down", trend.direction
    assert_equal "var(--color-destructive)", trend.color
  end

  test "flat" do
    trend1 = Trend.new(current: 100, previous: 100)
    trend2 = Trend.new(current: 100, previous: nil)
    assert_equal "flat", trend1.direction
    assert_equal "up", trend2.direction
    assert_equal "var(--color-gray)", trend1.color
  end

  test "infinitely up" do
    trend = Trend.new(current: 100, previous: 0)
    assert_equal "up", trend.direction
  end

  test "infinitely down" do
    trend = Trend.new(current: 0, previous: 100)
    assert_equal "down", trend.direction
  end
end