Test Adapter

The built-in Faraday Test adapter lets you define stubbed HTTP requests. This can be used to mock out network services in an application's unit tests.

The easiest way to do this is to create the stubbed requests when initializing a Faraday::Connection. Stubbing a request by path yields a block with a Faraday::Env object. The stub block expects an Array return value with three values: an Integer HTTP status code, a Hash of key/value headers, and a response body.

conn = Faraday.new do |builder|
  builder.adapter :test do |stub|
    # block returns an array with 3 items:
    # - Integer response status
    # - Hash HTTP headers
    # - String response body
    stub.get('/ebi') do |env|
      [
        200,
        { 'Content-Type': 'text/plain', },
        'shrimp'
      ]
    end

    # test exceptions too
    stub.get('/boom') do
      raise Faraday::ConnectionFailed
    end
  end
end

You can define the stubbed requests outside of the test adapter block:

stubs = Faraday::Adapter::Test::Stubs.new do |stub|
  stub.get('/tamago') { |env| [200, {}, 'egg'] }
end

This Stubs instance can be passed to a new Connection:

conn = Faraday.new do |builder|
  builder.adapter :test, stubs do |stub|
    stub.get('/ebi') { |env| [ 200, {}, 'shrimp' ]}
  end
end

It's also possible to stub additional requests after the connection has been initialized. This is useful for testing.

stubs.get('/uni') { |env| [ 200, {}, 'urchin' ]}

You can also stub the request body with a string or a proc. It would be useful to pass a proc if it's OK only to check the parts of the request body are passed.

stubs.post('/kohada', 'where=sea&temperature=24') { |env| [ 200, {}, 'spotted gizzard shad' ]}
stubs.post('/anago', -> (request_body) { JSON.parse(request_body).slice('name') == { 'name' => 'Wakamoto' } }) { |env| [200, {}, 'conger eel'] }

If you want to stub requests that exactly match a path, parameters, and headers, strict_mode would be useful.

stubs = Faraday::Adapter::Test::Stubs.new(strict_mode: true) do |stub|
  stub.get('/ikura?nori=true', 'X-Soy-Sauce' => '5ml' ) { |env| [200, {}, 'ikura gunkan maki'] }
end

This stub expects the connection will be called like this:

conn.get('/ikura', { nori: 'true' }, { 'X-Soy-Sauce' => '5ml' } )

If there are other parameters or headers included, the Faraday Test adapter will raise Faraday::Test::Stubs::NotFound. It also raises the error if the specified parameters (nori) or headers (X-Soy-Sauce) are omitted.

You can also enable strict_mode after initializing the connection. In this case, all requests, including ones that have been already stubbed, will be handled in a strict way.

stubs.strict_mode = true

Finally, you can treat your stubs as mocks by verifying that all of the stubbed calls were made. NOTE: this feature is still fairly experimental. It will not verify the order or count of any stub.

stubs.verify_stubbed_calls

After the test case is completed (possibly in an after hook), you should clear the default connection to prevent it from being cached between different tests. This allows for each test to have its own set of stubs

Faraday.default_connection = nil

Examples

Working RSpec and test/unit examples for a fictional JSON API client are available.