HTTP adapter for stubbing requests in tests.

Point a Dowser.Client.Config at this adapter (http_adapter: Dowser.Client.HTTP.Stub) and script its responses with stub/1, so a test exercises the full Dowser.Client request/response pipeline — URL building, headers, retries, JSON encoding/decoding — without a real search backend running.

The stub is stored in the calling process: stub/1 must run in the same process that performs the request (true for a plain ExUnit test body), and each process gets its own stub with no shared/global state, so tests can run async: true. If your code makes requests from another process (e.g. a GenServer), call stub/1 from that process instead.

body, as received by the stub function, is the already-encoded request body — iodata, not necessarily a flat binary — same as any Dowser.Client.HTTP.Adapter receives it; use IO.iodata_to_binary/1 before comparing it to a string.

Examples

test "indexes a document" do
  Dowser.Client.HTTP.Stub.stub(fn :put, url, _headers, body, _opts ->
    assert url == "http://localhost:9200/my-index/_doc/1"
    assert IO.iodata_to_binary(body) == ~s({"title":"hello"})

    Dowser.Client.HTTP.Stub.json(201, %{"_id" => "1", "result" => "created"})
  end)

  config = Dowser.Client.Config.new(endpoint: "http://localhost:9200", http_adapter: __MODULE__)

  assert {:ok, %{status: 201, body: %{"result" => "created"}}} =
           Dowser.Client.put("/my-index/_doc/1", %{title: "hello"}, config: config)
end

A single stub/1 handles every request made by the process for the rest of the test; call it again to change behaviour partway through, or have the function branch on method/url to script multiple endpoints:

Dowser.Client.HTTP.Stub.stub(fn
  :get, "http://localhost:9200/my-index/_search", _headers, _body, _opts ->
    Dowser.Client.HTTP.Stub.json(200, %{"hits" => %{"hits" => []}})

  :post, "http://localhost:9200/_bulk", _headers, _body, _opts ->
    Dowser.Client.HTTP.Stub.json(200, %{"errors" => false})
end)