Property Testing

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beancount_ex ships generative-testing infrastructure built on StreamData. The generators live in Beancount.Property (compiled only in the :test and :dev environments).

Generators

  • account/0 - valid account names such as Assets:Bank.
  • currency/0 - commodity codes.
  • date/0 - Date values within a bounded range.
  • amount/0 - positive Decimal amounts.
  • metadata/0 - small metadata maps.
  • balanced_transaction/0 - transactions whose postings always sum to zero.
  • ledger/0 - a complete, valid ledger: open directives for every account used, followed by a balanced transaction.

Properties

use ExUnitProperties

property "balanced transactions always render" do
  check all txn <- Beancount.Property.balanced_transaction() do
    assert is_binary(Beancount.render([txn]))
  end
end

property "rendering is deterministic" do
  check all ledger <- Beancount.Property.ledger() do
    assert Beancount.render(ledger) == Beancount.render(ledger)
  end
end

The suite verifies the core invariants:

  • balanced transactions always render to a binary,
  • rendering is deterministic,
  • generated ledgers declare an open for every account used, and
  • (integration, tagged :beancount) generated ledgers pass bean-check.

Oracle comparison

Beancount.Compare.compare/3 asserts that two engines produce equivalent normalized results for identical inputs. See Oracle Strategy.