test_that(
  "amr_cusum returns the expected output",
  {

    x <- c(
      0.20,
      0.21,
      0.22,
      0.30,
      0.40,
      0.45
    )

    result <- amr_cusum(x)

    expect_s3_class(
      result,
      "data.frame"
    )

    expect_equal(
      nrow(result),
      length(x)
    )

    expect_true(
      all(
        c(
          "observation",
          "observed",
          "cusum",
          "target",
          "threshold",
          "alert"
        ) %in% names(result)
      )
    )
  }
)


test_that(
  "amr_cusum preserves observations",
  {

    x <- c(
      0.10,
      0.15,
      0.20,
      0.25
    )

    result <- amr_cusum(x)

    expect_equal(
      result$observed,
      x
    )
  }
)


test_that(
  "amr_cusum starts at zero or positive value",
  {

    x <- c(
      0.10,
      0.10,
      0.10,
      0.10
    )

    result <- amr_cusum(
      x,
      target = 0.10
    )

    expect_true(
      all(result$cusum >= 0)
    )
  }
)


test_that(
  "amr_cusum detects sustained increase",
  {

    x <- c(
      0.10,
      0.10,
      0.10,
      0.50,
      0.60,
      0.70,
      0.80
    )

    result <- amr_cusum(
      x,
      target = 0.10,
      k = 0,
      h = 0.5
    )

    expect_true(
      any(result$alert)
    )
  }
)


test_that(
  "amr_cusum rejects non-numeric input",
  {

    expect_error(
      amr_cusum(
        c("R", "S", "R")
      )
    )
  }
)


test_that(
  "amr_cusum rejects missing values",
  {

    expect_error(
      amr_cusum(
        c(0.10, NA, 0.20)
      )
    )
  }
)