test_that(
  glue::glue(
    "convert_units() works with all possible input unit arguments (i.e. 'in' ",
    "or 'inches' on single measures"
  ),
  {
    # 1in is 2.54cm, and the possible names are "in", "inches", "cm", or
    # "centimeters"
    expect_equal(convert_units(2.54, "cm", "in"), 1)
    expect_equal(convert_units(2.54, "cm", "inches"), 1)
    expect_equal(convert_units(2.54, "centimeters", "in"), 1)
    expect_equal(convert_units(2.54, "centimeters", "inches"), 1)
  }
)

test_that(
  glue::glue(
    "convert_units() works with all possible input unit arguments (i.e. 'in' ",
    "or 'inches' on data frames"
  ),
  {
    # Make a test data frame
    test_df <- data.frame(
      x = rep(1, 3),
      y = rep(2, 3),
      z = c("a", "b", "c")
    )

    # Create the expected outcome data frame
    expected_df <- data.frame(
      x = rep(2.54, 3),
      y = rep(5.08, 3),
      z = c("a", "b", "c")
    )

    # Run the tests
    expect_identical(
      convert_units(test_df, "in", "cm", c("x", "y")),
      expected_df
    )
    expect_identical(
      convert_units(test_df, "in", "centimeters", c("x", "y")),
      expected_df
    )
    expect_identical(
      convert_units(test_df, "inches", "cm", c("x", "y")),
      expected_df
    )
    expect_identical(
      convert_units(test_df, "inches", "centimeters", c("x", "y")),
      expected_df
    )
  }
)

test_that(
  "convert_units() skips non-numeric and non-integer columns successfully",
  {
    # Make a test data frame
    test_df <- data.frame(
      x = rep(1, 3),
      y = rep(2, 3),
      z = c("a", "b", "c")
    )

    # Create the expected outcome data frame
    expected_df <- data.frame(
      x = rep(2.54, 3),
      y = rep(5.08, 3),
      z = c("a", "b", "c")
    )

    # Run the test
    suppressMessages(
      expect_identical(
        convert_units(test_df, "in", "centimeters", c("x", "y", "z")),
        expected_df
      )
    )
  }
)

test_that("convert_units() errors when input or output units are unavailable", {
  # If a made-up unit, like "foo" or "bar" are passed as either input units or
  # output units, the function should error
  expect_error(convert_units(2.54, "foo", "bar"))
  expect_error(convert_units(2.54, "foo", "in"))
  expect_error(convert_units(2.54, "cm", "bar"))
})

test_that(
  glue::glue(
    "convert_units() errors when a data frame is supplied with no ",
    "conversion_columns argument"
  ),
  {
    # Make a test data frame
    test_df <- data.frame(
      x = 1:5,
      y = 6:10,
      z = c("a", "b", "c", "d", "e")
    )

    # Produce the error
    expect_error(convert_units(test_df, "ft", "m"))
  }
)

test_that(
  glue::glue(
    "convert_units() messages user when a column supplied in ",
    "conversion_columns is not in the data frame"
  ),
  {
    # Make a test data frame
    test_df <- data.frame(
      x = 1:5,
      y = 6:10,
      z = c("a", "b", "c", "d", "e")
    )

    # Produce the message
    expect_message(
      convert_units(
        test_df,
        "ft",
        "m",
        conversion_columns = c("x", "y", "a")
      )
    )
  }
)