test_that("calculate_incidence works correctly", {
  # Test 1: Typical data
  mydata <- data.frame(
    ID = c("Greag", "Kristma", "Alex", "Jaminae", "Munroe", "Peteo"),
    Enrollment = as.Date(c("2023-03-10", "2023-02-02", "2023-01-01",
                           "2023-02-02", "2023-01-01", "2023-01-04")),
    End = as.Date(c("2023-08-10", "2023-07-14", "2023-06-12",
                    "2023-05-13", "2023-05-12", "2023-12-31")),
    Censored = c(1, 0, 0, 0, 1, 1)
  )

  result <- incidence(mydata)

  # Define the expected result
  expected <- "The incidence rate is 2.8  new cases per 1000 person_days or approximately 85 new cases per 1000 person-months"
  # Compare the actual result to the expected result
  expect_equal(result, expected)
})

test_that("calculate_incidence handles missing required columns", {
  # Test 1: Critical columns missing.
  mydata <- data.frame(
    ID = c("Greag", "Kristma", "Alex", "Jaminae", "Munroe", "Peteo"),
    Enrollment = as.Date(c("2023-03-10", "2023-02-02", "2023-01-01",
                           "2023-02-02", "2023-01-01", "2023-01-04")),
    Ends = as.Date(c("2023-08-10", "2023-07-14", "2023-06-12", # Intentional typo "Ends"
                     "2023-05-13", "2023-05-12", "2023-12-31")),
    Censored = c(1, 0, 0, 0, 1, 1)
  )

  expect_error(
    incidence(mydata),
    "One or more required columns not found in the dataframe"
  )
})

test_that("calculate_incidence handles end dates preceding start dates", {
  # Test 1: Exit date preceding the entry date
  mydata <- data.frame(
    ID = c("Greag", "Kristma", "Alex", "Jaminae", "Munroe", "Peteo"),
    Enrollment = as.Date(c("2023-03-10", "2023-02-02", "2023-01-01",
                           "2023-02-02", "2023-01-01", "2023-01-04")),
    End = as.Date(c("2023-02-10", "2023-07-14", "2023-06-12", # Intentional error
                    "2023-05-13", "2023-05-12", "2023-12-31")),
    Censored = c(1, 0, 0, 0, 1, 1)
  )

  expect_error(
    incidence(mydata),
    "One or more of the participant end dates precede the start date. Please check that out."
  )
})