skip_if_not_installed("car")

mod <- lm(mpg ~ disp + hp, mtcars)
x <- car::deltaMethod(mod, "disp + hp", rhs = 0)

test_that("ci", {
  expect_equal(ci(x)$CI_low, x$`2.5 %`, tolerance = 1e-3)
})

test_that("se", {
  expect_equal(standard_error(x)$SE, x$SE, tolerance = 1e-3)
})

test_that("p", {
  expect_equal(p_value(x)$p, x$`Pr(>|z|)`, tolerance = 1e-3)
})

mp <- model_parameters(x)
test_that("model_parameters", {
  expect_equal(mp$Coefficient, x$Estimate, tolerance = 1e-3)
  expect_equal(mp$Parameter, row.names(x), tolerance = 1e-3)
})


x <- car::deltaMethod(mod, "disp + hp", rhs = 0, level = 0.8)

test_that("ci", {
  expect_equal(ci(x)$CI_low, x$`10 %`, tolerance = 1e-3)
})

mp <- model_parameters(x)
test_that("model_parameters", {
  expect_equal(attributes(mp)$ci, 0.8, tolerance = 1e-3)
})