test_that("coef path returns every stored beta solution", {
  beta_matrix <- matrix(
    c(0, 0,
      1, 0,
      2, 3),
    nrow = 3,
    byrow = TRUE,
    dimnames = list(NULL, c("x1", "x2"))
  )
  path_details <- structure(
    list(
      beta_matrix = beta_matrix,
      # Ensure the implementation does not partially match beta_mat.
      beta_mat = matrix(99, nrow = 1, ncol = 2)
    ),
    class = "autotune_lasso_path"
  )
  fit <- structure(
    list(
      beta = beta_matrix[3, ],
      a0 = 4,
      nvars = 2,
      CD.path.details = path_details
    ),
    class = "autotune_lasso"
  )

  result <- coef(fit, path = TRUE, intercept = FALSE)

  expect_s4_class(result, "dgCMatrix")
  expect_equal(dim(result), c(2L, 3L))
  expect_equal(unname(as.matrix(result)), unname(t(beta_matrix)))
  expect_identical(colnames(result), c("lambda_1", "lambda_2", "final_lambda"))
  expect_identical(rownames(result), c("x1", "x2"))
})

test_that("path coefficients include an intercept for every solution", {
  beta_matrix <- matrix(c(1, 2, 3, 4), nrow = 2, byrow = TRUE)
  path_details <- structure(
    list(beta_matrix = beta_matrix),
    class = "autotune_lasso_path"
  )
  fit <- structure(
    list(
      beta = beta_matrix[2, ],
      a0 = 2,
      nvars = 2,
      CD.path.details = path_details
    ),
    class = "autotune_lasso"
  )

  result <- coef(fit, path = TRUE)

  expect_equal(dim(result), c(3L, 2L))
  expect_equal(as.numeric(result[1, ]), c(2, 2))
  expect_equal(unname(as.matrix(result[-1, ])), unname(t(beta_matrix)))
})

test_that("the registered path method dispatches through coef generic", {
  beta_matrix <- matrix(seq_len(6), nrow = 3, byrow = TRUE)
  path_details <- structure(
    list(beta_matrix = beta_matrix),
    class = "autotune_lasso_path"
  )

  result <- coef(path_details, intercept = FALSE)

  expect_equal(unname(as.matrix(result)), unname(t(beta_matrix)))
})

test_that("path FALSE continues to return only the final solution", {
  beta_matrix <- matrix(c(1, 0, 2, 3), nrow = 2, byrow = TRUE)
  fit <- structure(
    list(
      beta = beta_matrix[2, ],
      a0 = 5,
      nvars = 2,
      CD.path.details = structure(
        list(beta_matrix = beta_matrix),
        class = "autotune_lasso_path"
      )
    ),
    class = "autotune_lasso"
  )

  result <- coef(fit, path = FALSE, intercept = FALSE, sparse = FALSE)

  expect_equal(unname(result), beta_matrix[2, ])
})