silver-octo-spoon/wolverine/a-frame-architecture/FinancialApi.Application.UnitTests/ApplyFeeHandlerTests.cs

using System.Security.Cryptography;
using FinancialApi.Application.Commands;
using FinancialApi.Application.Handlers;
using FinancialApi.Application.Models;
using FinancialApi.Domain;
using FinancialApi.Domain.Entities;
using FluentAssertions;
using FluentAssertions.Execution;

namespace FinancialApi.Application.UnitTests;

public class ApplyFeeHandlerTests
{
    [Fact]
    public void GivenValidAccounts_BasicFee_ShouldValidateEverything()
    {
        // Arrange
        var command = new ApplyFeeCommand(1, 100);
        var account = new Account(1, 100, AccountType.Debit);
        var revenueAccount = new Account(99999, 0, AccountType.Credit);
        var pair = new FeeContext(account, revenueAccount, TimeProvider.System.GetUtcNow());

        // Act
        var intents = ApplyFeeHandler.Handle(command, pair);

        // Assert
        using var _ = new AssertionScope();
        intents.CustomerWrite.Entity.Balance.Should()
            .Be(account.Balance - command.Amount);
        intents.RevenueWrite.Entity.Balance.Should()
            .Be(revenueAccount.Balance + command.Amount);
        intents.JournalWrite.Entity.Lines.Count.Should()
            .BeGreaterThanOrEqualTo(2);
        intents.Event.AccountId.Should()
            .Be(account.Id);
        intents.Event.Amount.Should()
            .Be(command.Amount);
    }

    public class LiabilityAccount
    {
        [Theory]
        [InlineData(100.0, 20.0, 80.0)]
        [InlineData(199.78, 10.0, 189.78)]
        [InlineData(200000, 0.09, 199999.91)]
        [InlineData(1000, 1000, 0)]
        public void GivenStartingBalanceGreaterThanFee_ApplyFee_ShouldBeExpectedBalance(
            decimal startingBalance,
            decimal feeAmount,
            decimal expectedBalance
        )
        {
            var command = new ApplyFeeCommand(1, feeAmount);
            var account = new Account(1, startingBalance, AccountType.Liability);
            var revenueAccount = new Account(99999, 0, AccountType.Credit);
            var pair = new FeeContext(account, revenueAccount, TimeProvider.System.GetUtcNow());

            // Act
            var intents = ApplyFeeHandler.Handle(command, pair);

            // Assert
            using var _ = new AssertionScope();
            intents.CustomerWrite.Entity.Balance.Should()
                .Be(expectedBalance);
        }

        [Theory]
        [InlineData(100.0, 110.0)]
        [InlineData(199.78, 200.0)]
        [InlineData(200000, 200000.01)]
        [InlineData(1000, 1999999)]
        public void GivenStartingBalanceLessThanFee_ApplyFee_ShouldFail(decimal startingBalance, decimal feeAmount)
        {
            var command = new ApplyFeeCommand(1, feeAmount);
            var account = new Account(1, startingBalance, AccountType.Liability);
            var revenueAccount = new Account(99999, 0, AccountType.Credit);
            var pair = new FeeContext(account, revenueAccount, TimeProvider.System.GetUtcNow());

            // Act
            var act = () => ApplyFeeHandler.Handle(command, pair);

            // Assert
            using var _ = new AssertionScope();
            act.Should()
                .Throw<InsufficientFundsException>();
            account.Balance.Should()
                .Be(startingBalance);
            revenueAccount.Balance.Should()
                .Be(0);
        }
    }

    public class CreditAccount
    {
        [Theory]
        [InlineData(100.0, 20.0, 80.0)]
        [InlineData(199.78, 10.0, 189.78)]
        [InlineData(200000, 0.09, 199999.91)]
        [InlineData(1000, 1000, 0)]
        public void GivenStartingBalanceGreaterThanFee_ApplyFee_ShouldBeExpectedBalance(
            decimal startingBalance,
            decimal feeAmount,
            decimal expectedBalance
        )
        {
            var command = new ApplyFeeCommand(1, feeAmount);
            var account = new Account(1, startingBalance, AccountType.Credit);
            var revenueAccount = new Account(99999, 0, AccountType.Credit);
            var pair = new FeeContext(account, revenueAccount, TimeProvider.System.GetUtcNow());

            // Act
            var intents = ApplyFeeHandler.Handle(command, pair);

            // Assert
            using var _ = new AssertionScope();
            intents.CustomerWrite.Entity.Balance.Should()
                .Be(expectedBalance);
        }

        [Theory]
        [InlineData(100.0, 110.0, -10.0)]
        [InlineData(199.78, 200.0, -0.22)]
        [InlineData(200000, 200000.01, -0.01)]
        [InlineData(1000, 1999999, -1998999)]
        public void GivenStartingBalanceLessThanFee_ApplyFee_ShouldBeExpectedBalance(
            decimal startingBalance,
            decimal feeAmount,
            decimal expectedBalance
        )
        {
            var command = new ApplyFeeCommand(1, feeAmount);
            var account = new Account(1, startingBalance, AccountType.Credit);
            var revenueAccount = new Account(99999, 0, AccountType.Credit);
            var pair = new FeeContext(account, revenueAccount, TimeProvider.System.GetUtcNow());

            // Act
            var intents = ApplyFeeHandler.Handle(command, pair);

            // Assert
            using var _ = new AssertionScope();
            intents.CustomerWrite.Entity.Balance.Should()
                .Be(expectedBalance);
        }
    }
}