mockth

Gleam modules mocking library. This is a simple wrapper around Erlang Meck library.

gleam add mockth

Usage

It provides a simple API to mock Gleam modules and functions. All you need to use mockth.expect function to mock any external function with your own implementation.

import gleeunit
import gleeunit/should
import gleam/function
import mockth

pub fn main() {
 gleeunit.main()
}

pub fn expect_test() {
 let assert Ok(_) =
   mockth.expect("gleam@function", "identity", fn(_) { "hello" })

 mockth.validate("gleam@function")
 |> should.equal(True)

 mockth.mocked()
 |> should.equal(["gleam@function"])

 function.identity("world")
 |> should.equal("hello")

 mockth.unload_all()
}

Don’t forget to unload all mocks after each test case.

Further documentation can be found at https://hexdocs.pm/mockth.

With use sugar

The with_mock function is available to use mockth in your tests with the use sugar. It performs all steps from the example above (mock, validate, assert module is mocked), and even unloads all mocks after the test function finishes.

pub fn with_mock_test() {
 use mock <- mockth.with_mock(
   module: "gleam@function",
   function: "identity",
   replacement: fn(_) { "hello" },
 )

 function.identity("world")
 |> should.equal("hello")

 // the mocked module is available here as `mocks`
 // for example to be able to call `mockth.history` with it.
}

Development

gleam run   # Run the project
gleam test  # Run the tests
gleam shell # Run an Erlang shell