test_that(
  "amr_trend calculates monthly trends",
  {

    dat <- data.frame(
      date = as.Date(c(
        "2025-01-05",
        "2025-01-15",
        "2025-02-05",
        "2025-02-15",
        "2025-03-05"
      )),
      AMP = c(
        "R",
        "S",
        "R",
        "R",
        "S"
      )
    )

    result <- amr_trend(
      data = dat,
      date = date,
      outcome = AMP
    )

    expect_s3_class(
      result,
      "data.frame"
    )

    expect_equal(
      result$time,
      c(
        "2025-01",
        "2025-02",
        "2025-03"
      )
    )

    expect_equal(
      result$tested,
      c(2, 2, 1)
    )

    expect_equal(
      result$resistant,
      c(1, 2, 0)
    )

    expect_equal(
      result$resistance_percent,
      c(50, 100, 0)
    )
  }
)


test_that(
  "amr_trend supports quarterly aggregation",
  {

    dat <- data.frame(
      date = as.Date(c(
        "2025-01-01",
        "2025-02-01",
        "2025-04-01",
        "2025-07-01"
      )),
      AMP = c(
        "R",
        "S",
        "R",
        "S"
      )
    )

    result <- amr_trend(
      data = dat,
      date = date,
      outcome = AMP,
      period = "quarter"
    )

    expect_equal(
      result$time,
      c(
        "2025-Q1",
        "2025-Q2",
        "2025-Q3"
      )
    )

    expect_equal(
      result$tested,
      c(2, 1, 1)
    )
  }
)


test_that(
  "amr_trend supports annual aggregation",
  {

    dat <- data.frame(
      date = as.Date(c(
        "2024-01-01",
        "2024-06-01",
        "2025-01-01"
      )),
      AMP = c(
        "R",
        "S",
        "R"
      )
    )

    result <- amr_trend(
      data = dat,
      date = date,
      outcome = AMP,
      period = "year"
    )

    expect_equal(
      result$time,
      c(
        "2024",
        "2025"
      )
    )

    expect_equal(
      result$tested,
      c(2, 1)
    )
  }
)


test_that(
  "amr_trend removes missing outcomes",
  {

    dat <- data.frame(
      date = as.Date(c(
        "2025-01-01",
        "2025-01-02",
        "2025-02-01"
      )),
      AMP = c(
        "R",
        NA,
        "S"
      )
    )

    result <- amr_trend(
      data = dat,
      date = date,
      outcome = AMP
    )

    expect_equal(
      result$tested,
      c(1, 1)
    )

    expect_equal(
      result$resistant,
      c(1, 0)
    )
  }
)


test_that(
  "amr_trend rejects invalid period",
  {

    dat <- data.frame(
      date = as.Date("2025-01-01"),
      AMP = "R"
    )

    expect_error(
      amr_trend(
        data = dat,
        date = date,
        outcome = AMP,
        period = "week"
      )
    )
  }
)


test_that(
  "amr_trend rejects missing columns",
  {

    dat <- data.frame(
      date = as.Date("2025-01-01"),
      AMP = "R"
    )

    expect_error(
      amr_trend(
        data = dat,
        date = wrong_date,
        outcome = AMP
      ),
      "Date column"
    )

    expect_error(
      amr_trend(
        data = dat,
        date = date,
        outcome = wrong_outcome
      ),
      "Outcome column"
    )
  }
)


test_that(
  "amr_trend rejects invalid dates",
  {

    dat <- data.frame(
      date = c(
        "not-a-date",
        "2025-01-01"
      ),
      AMP = c(
        "R",
        "S"
      )
    )

    expect_error(
      amr_trend(
        data = dat,
        date = date,
        outcome = AMP
      ),
      "invalid or missing dates"
    )
  }
)