BDD_like_take2.cs

private Account _account;
private decimal _openingBalance = 2500m;
private decimal _positiveAmount = 1000m;

private void Given_account_with_positive_balance()
{
  string name = "Account Name";
  string description = "Account Description";

  _account = new Account(name, description, _openingBalance);
}

private void When_deposit_positive_amount()
{
  _account.Deposit(_positiveAmount);
}

[Test]
public void Can_deposit_positive_amounts()
{
  Given_account_with_positive_balance();

  When_deposit_positive_amount();

  // Then
  // 1. Current balance should increase by deposited amount
  Assert.AreEqual(_openingBalance, _account.OpeningBalance);
  // 2. Opening balance should stay the same
  Assert.AreEqual(_openingBalance + _positiveAmount, _account.CurrentBalance);
}

This is second take of the BDD-like test case.
Using meaningful method names that can be reused in building different scenarios.