double v0.6.5 Double

Double builds on-the-fly injectable dependencies for your tests. It does NOT override behavior of existing modules or functions. Double uses Elixir’s built-in language features such as pattern matching and message passing to give you everything you would normally need a complex mocking tool for.

Summary

Functions

Adds a stubbed function to the given map, struct, or module. Structs will fail if they are missing the key given for function_name. Modules will fail if the function is not defined

Clears stubbed functions from a double. By passing no arguments (or nil) all functions will be cleared. A single function name (atom) or a list of function names can also be given

Returns a map that can be used to setup stubbed functions

Same as double/0 but can return structs and modules too

Invoked when the server is started. start_link/3 or start/3 will block until it returns

Types

allow_option()
allow_option ::
  {:with, [...]} |
  {:returns, any} |
  {:raises, String.t | {atom, String.t}}
double_option()
double_option() :: {:verify, true | false}

Functions

allow(dbl, function_name)

Adds a stubbed function to the given map, struct, or module. Structs will fail if they are missing the key given for function_name. Modules will fail if the function is not defined.

allow(dbl, function_name, func_opts)
allow(any, atom, function | [allow_option]) ::
  struct |
  map |
  atom
clear(dbl, function_name \\ nil)
clear(any, atom | list) :: struct | map | atom

Clears stubbed functions from a double. By passing no arguments (or nil) all functions will be cleared. A single function name (atom) or a list of function names can also be given.

double()
double() :: map

Returns a map that can be used to setup stubbed functions.

double(source, opts \\ [verify: true])
double(atom, [double_option]) :: atom
double(struct, [double_option]) :: struct

Same as double/0 but can return structs and modules too

init(list)

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be (re)started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

  • The GenServer is disabled by configuration but might be enabled later.
  • An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.