# --- Unit Tests for fittingFunction ---

test_that("fittingFunction calculates the squared difference correctly", {
  # Test with known values to check the basic calculation
  expect_equal(
    fittingFunction(
      lambda = 2, q = 0.5,
      nu = 2, SigmaSquaredHat = 10
    ),
    50.6176743
  )

  # Another test case
  expect_equal(
    fittingFunction(
      lambda = 5, q = 0.1,
      nu = 4, SigmaSquaredHat = 5
    ),
    5.9006287
  )
})

test_that("fittingFunction output is always non-negative", {
  # The result is squared so it should never be less than zero

  # Case where sigmaSquaredHat is larger
  result1 <- fittingFunction(
    lambda = 2, q = 0.5,
    nu = 2, SigmaSquaredHat = 10
  )
  expect_gte(result1, 0) # gte means "greater than or equal to"

  # Case where sigmaSquaredHat is smaller
  result2 <- fittingFunction(
    lambda = 10, q = 0.1,
    nu = 2, SigmaSquaredHat = 1
  )
  expect_gte(result2, 0)
})