testthat::test_that("extend: add method", {

  m <- modules::module({
    fun <- identity
  })

  m <- modules::extend(m, {
    fun1 <- identity
  })

  testthat::expect_equal(m$fun1(m$fun(1)), 1)

})

testthat::test_that("extend: override method", {

  m <- modules::module({
    fun <- identity
  })

  m <- modules::extend(m, {
    fun <- function(x) 2 * x
  })

  testthat::expect_equal(m$fun(1), 2)

})

testthat::test_that("extend: nested definitions", {

  m <- extend(
    extend(
      modules::module({
        fun <- identity
      }),
      {fun <- identity}
    ),
    {fun <- identity}
  )

  testthat::expect_equal(m$fun(1), 1)

})

testthat::test_that("extend a module from file -- see #16", {
  ## just to verify, that standard behavior works:
  m <- modules::module({
    export("bar")
    bar <- function() "bar"
    foo <- function() "foo"
  })
  modules::extend(m, {
    testthat::expect_equal(foo(), "foo")
  })

  ## now from the file:
  fileName <- tempfile(fileext = ".R")
  on.exit(file.remove(fileName))
  writeLines(c(
    'export("bar")', 'bar <- function() "bar"', 'foo <- function() "foo"'),
    fileName)
  m <- modules::use(fileName)
  modules::extend(m, {
    testthat::expect_equal(foo(), "foo")
  })
})