test_that(
  "amr_ewma returns the expected output",
  {

    x <- c(
      0.20,
      0.21,
      0.19,
      0.22,
      0.23,
      0.25,
      0.40,
      0.45
    )

    result <- amr_ewma(x)

    expect_s3_class(
      result,
      "data.frame"
    )

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

    expect_true(
      all(
        c(
          "observation",
          "observed",
          "ewma",
          "center",
          "upper_limit",
          "lower_limit",
          "alert"
        ) %in% names(result)
      )
    )
  }
)


test_that(
  "amr_ewma preserves observations",
  {

    x <- c(
      0.10,
      0.15,
      0.20,
      0.25,
      0.30
    )

    result <- amr_ewma(x)

    expect_equal(
      result$observed,
      x
    )
  }
)


test_that(
  "amr_ewma produces finite EWMA values",
  {

    x <- c(
      0.10,
      0.12,
      0.15,
      0.20,
      0.25
    )

    result <- amr_ewma(x)

    expect_true(
      all(is.finite(result$ewma))
    )

    expect_true(
      all(is.finite(result$upper_limit))
    )

    expect_true(
      all(is.finite(result$lower_limit))
    )
  }
)


test_that(
  "amr_ewma rejects invalid lambda",
  {

    x <- c(
      0.10,
      0.20,
      0.30
    )

    expect_error(
      amr_ewma(
        x,
        lambda = 0
      )
    )

    expect_error(
      amr_ewma(
        x,
        lambda = 1.5
      )
    )
  }
)


test_that(
  "amr_ewma rejects missing values",
  {

    x <- c(
      0.10,
      NA,
      0.30
    )

    expect_error(
      amr_ewma(x)
    )
  }
)


test_that(
  "amr_ewma requires at least three observations",
  {

    expect_error(
      amr_ewma(
        c(0.10, 0.20)
      )
    )
  }
)