skip_if_not_installed("lme4")

data(sleepstudy, package = "lme4")

m1 <- lm(mpg ~ 0 + gear, data = mtcars)
m2 <- lm(mpg ~ gear, data = mtcars)
m3 <- suppressWarnings(lme4::lmer(Reaction ~ 0 + Days + (Days | Subject), data = sleepstudy))
m4 <- lme4::lmer(Reaction ~ Days + (Days | Subject), data = sleepstudy)
m5 <- suppressWarnings(lme4::lmer(Reaction ~ 0 + (Days | Subject), data = sleepstudy))

m6 <- lm(Sepal.Length ~ 0 + Petal.Width + Species, data = iris)
m7 <- lm(Sepal.Length ~ -1 + Petal.Width + Species, data = iris)
m8 <- lm(Sepal.Length ~ Petal.Width + Species, data = iris)
m9 <- lm(Sepal.Length ~ Petal.Width + Species + 1, data = iris)

test_that("has_intercept", {
  expect_true(has_intercept(m2))
  expect_false(has_intercept(m1))
  expect_true(has_intercept(m4))
  expect_false(has_intercept(m3))
  expect_false(has_intercept(m5))
  expect_false(has_intercept(m6))
  expect_false(has_intercept(m7))
  expect_true(has_intercept(m8))
  expect_true(has_intercept(m9))
})