added code to test interface logic checks

Author: topepo

tests/testthat/test_fit_interfaces.R

@@ -0,0 +1,32 @@
+library(testthat)
+library(parsnip)
+library(recipes)
+library(rlang)
+
+rec <- recipe(~ ., data = iris)
+f <- y ~ x
+
+tester <-
+  function(object, formula = NULL, recipe = NULL, x = NULL, y = NULL, data = NULL)
+    parsnip:::check_interface(formula, recipe, x, y, data, match.call(expand.dots = TRUE))
+
+test_that('good args', {
+  expect_equal(tester(NULL, formula = f, data = iris), "formula")
+  expect_equal(tester(NULL, recipe = rec, data = iris), "recipe")
+  expect_equal(tester(NULL, x = iris, y = iris), "xy")
+  expect_equal(tester(NULL, f, data = iris), "formula")
+  expect_equal(tester(NULL, formula = f, data = iris, y = iris), "formula")
+})
+
+test_that('unnamed args', {
+  expect_error(tester(NULL, rec, data = iris))
+  expect_error(tester(NULL, iris, y = iris))
+  expect_error(tester(NULL, data = iris))
+})
+
+test_that('wrong args', {
+  expect_error(tester(NULL, x = iris, data = iris))
+  expect_error(tester(NULL, f,  x = iris, y = iris, data = iris))
+})
+
+