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Testing Time Series Trend Analysis in Maybe Finance

This test suite validates the TimeSeries::Trend class functionality in the Maybe Finance application, focusing on trend calculations and directional indicators for financial data analysis. The tests verify proper handling of monetary trends, directional changes, and edge cases in time series data.

Test Coverage Overview

The test suite provides comprehensive coverage of trend analysis functionality, including:

Money trend calculations with percentage and value comparisons
Directional trend detection (up, down, flat)
Color coding based on trend direction
Edge cases including infinite trends and null values

Implementation Analysis

The testing approach utilizes Minitest’s assertion framework to validate trend calculations and directional logic. The implementation follows Ruby’s testing patterns with individual test cases for specific scenarios, leveraging ActiveSupport::TestCase for Rails integration.

The tests demonstrate proper isolation of concerns and clear separation of test cases for different trend scenarios.

Technical Details

Testing infrastructure includes:

Minitest as the primary testing framework
ActiveSupport::TestCase for Rails integration
Money class integration for financial calculations
Custom TimeSeries::Trend class implementation

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Comprehensive edge case coverage
Clear test case naming and organization
Isolated test scenarios
Consistent assertion patterns
Proper handling of nil values and boundary conditions

maybe-finance/maybe

test/models/time_series/trend_test.rb

            
require "test_helper"

class TimeSeries::TrendTest < ActiveSupport::TestCase
  test "handles money trend" do
    trend = TimeSeries::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 = TimeSeries::Trend.new(current: 100, previous: 50)
    assert_equal "up", trend.direction
    assert_equal "#10A861", trend.color
  end

  test "down" do
    trend = TimeSeries::Trend.new(current: 50, previous: 100)
    assert_equal "down", trend.direction
    assert_equal "#F13636", trend.color
  end

  test "flat" do
    trend1 = TimeSeries::Trend.new(current: 100, previous: 100)
    trend2 = TimeSeries::Trend.new(current: 100, previous: nil)
    trend3 = TimeSeries::Trend.new(current: nil, previous: nil)
    assert_equal "flat", trend1.direction
    assert_equal "flat", trend2.direction
    assert_equal "flat", trend3.direction
    assert_equal "#737373", trend1.color
  end

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

  test "infinitely down" do
    trend1 = TimeSeries::Trend.new(current: nil, previous: 100)
    trend2 = TimeSeries::Trend.new(current: 0, previous: 100)
    assert_equal "down", trend1.direction
    assert_equal "down", trend2.direction
  end

  test "empty" do
    trend = TimeSeries::Trend.new(current: nil, previous: nil)
    assert_equal "flat", trend.direction
  end
end