test_that("no errors or warnings with correct use", {

  expect_error(
    calc_predictive(
      y = c(7, 12), 
      n = c(50, 50), 
      N = c(100, 100), 
      p0 = NULL, 
      delta = 0,
      S = 100
    ),
    NA
  )

  expect_warning(
    calc_predictive(
      y = c(7, 12), 
      n = c(50, 50), 
      N = c(100, 100), 
      p0 = NULL, 
      delta = 0,
      S = 100
    ),
    NA
  )

  expect_error(
    calc_predictive(
      y = 14, 
      n = 50, 
      p0 = 0.2, 
      delta = NULL, 
      N = 100,
      S = 100
    ),
    NA
  )

  expect_warning(
    calc_predictive(
      y = 14, 
      n = 50, 
      p0 = 0.2, 
      delta = NULL,
      N = 100, 
      S = 100
    ),
    NA
  )
})

test_that("errors when expected", {

  expect_error(
    calc_predictive(
      y = c(7, 12), 
      n = 50, 
      N = c(100, 100), 
      S = 100
    )
  )

  expect_error(
    calc_predictive(
      y = c(7, 12), 
      n = c(50, 50), 
      N = c(100, 100),
      p0 = 0.1, 
      delta = 0, 
      S = 100
    )
  )

  expect_error(
    calc_predictive(
      p0 = 0.1, 
      y = c(7, 12), 
      n = c(50, 50), 
      N = c(100, 100),
      S = 100, 
      direction = "south"
    )
  )
  
  expect_error(
    calc_predictive(
      p0 = NULL,
      y = 14,
      n = 50,
      N = 100,
      S = 100,
      delta = 0 
    )
  )

  expect_error(
    calc_predictive(
      p0 = 0.2,
      y = c(14, 12), 
      n = c(50, 50),
      N = c(100, 100),
      S = 100,
      delta = NULL, 
    )
  )

  expect_error(
    calc_predictive(
      p0 = NULL, 
      y = 14, 
      n = 50, 
      delta = NULL, 
      N = 100,
      S = 100
    )
  )

  expect_error(
    calc_predictive(
      y = c(7, 12), 
      n = c(50, 50), 
      N = c(100, 100),
      S = 100, 
      delta = NULL
    ) 
  )

  expect_error(
    calc_predictive(
      y = c(7, 12), 
      n = c(50, 50), 
      N = 100, 
      p0 = NULL, 
      delta = 0,
      S = 100
    )
  )

})