Compare two floating point number equivalence testing methods

floating-equal.R

library(testthat)

# Method A: round to 6 significant digits, then compare with default tiny tolerance
equal_after_signif <- function(x, y) {
  expect_equal(signif(x, digits = 6), signif(y, digits = 6))
}

# Method B: compare with relative/absolute tolerance = 1e-6
equal_with_tolerance <- function(x, y) {
  expect_equal(x, y, tolerance = 1e-6)
}

test_that("Example 1: signif() says equal, tolerance says not equal", {
  x <- 1.000003
  y <- 1

  # Method A should succeed
  equal_after_signif(x, y)

  # Method B should fail
  expect_failure(equal_with_tolerance(x, y))
})

test_that("Example 2: tolerance says equal, signif() says not equal", {
  x <- 7.000006
  y <- 7

  # Method A should fail
  expect_failure(equal_after_signif(x, y))

  # Method B should succeed
  equal_with_tolerance(x, y)
})