Testing

Tink is designed to be easily testable. This guide covers unit testing with Mox, integration testing with Bypass, and using Tink's sandbox environment.

Unit Testing with Mox

Tink defines Tink.HTTPBehaviour so you can mock the HTTP layer:

# test/support/mocks.ex
Mox.defmock(Tink.HTTPMock, for: Tink.HTTPBehaviour)

# config/test.exs
config :tink,
  http_adapter:         Tink.HTTPMock,
  enable_rate_limiting: false,
  cache:                [enabled: false]

# test/my_feature_test.exs
defmodule MyFeatureTest do
  use ExUnit.Case, async: true
  import Mox

  setup :verify_on_exit!

  test "lists accounts" do
    Tink.HTTPMock
    |> expect(:get, fn _client, "/api/v1/accounts", _opts ->
      {:ok, %{
        "accounts" => [
          %{"id" => "acc_1", "name" => "Current Account", "balance" => 1500}
        ]
      }}
    end)

    {:ok, client} = Tink.Client.new(client_id: "test", client_secret: "test")
    assert {:ok, [%{id: "acc_1"}]} = Tink.Accounts.list(client)
  end
end

Integration Testing with Bypass

Use Bypass to run a local HTTP server that intercepts real Finch requests:

defmodule Tink.AccountsIntegrationTest do
  use ExUnit.Case

  setup do
    bypass = Bypass.open()
    client = Tink.Client.new!(
      client_id:     "test_id",
      client_secret: "test_secret",
      base_url:      "http://localhost:#{bypass.port}"
    )
    {:ok, bypass: bypass, client: client}
  end

  test "lists accounts", %{bypass: bypass, client: client} do
    Bypass.expect_once(bypass, "GET", "/api/v1/accounts", fn conn ->
      Plug.Conn.resp(conn, 200, Jason.encode!(%{
        "accounts" => [%{"id" => "acc_1", "name" => "Checking"}]
      }))
    end)

    assert {:ok, [%{id: "acc_1"}]} = Tink.Accounts.list(client)
  end
end

Sandbox Environment

Tink provides a sandbox for end-to-end testing without real banks:

# config/test.exs
config :tink,
  base_url:      "https://api.tink.com",   # Sandbox uses the same base URL
  client_id:     System.get_env("TINK_SANDBOX_CLIENT_ID"),
  client_secret: System.get_env("TINK_SANDBOX_CLIENT_SECRET")

In the sandbox you can use Tink's test providers (e.g. se-test-open-banking-redirect) to simulate bank connections without real credentials.

Test Helpers

Disable rate limiting and caching in tests to avoid flakiness:

# config/test.exs
config :tink,
  enable_rate_limiting: false,
  cache: [enabled: false],
  debug_mode: false

Property-Based Testing

Use stream_data to fuzz-test parameter handling:

defmodule Tink.ParamTest do
  use ExUnit.Case
  use ExUnitProperties

  property "list_transactions/2 never raises on arbitrary date strings" do
    check all date <- StreamData.string(:alphanumeric, max_length: 20) do
      result = Tink.Transactions.list(client(), date_from: date)
      assert match?({:ok, _} | {:error, %Tink.Error{}}, result)
    end
  end
end