diff --git a/tests/testthat/test-zero_crossings.R b/tests/testthat/test-zero_crossings.R
new file mode 100644
index 00000000..49385361
--- /dev/null
+++ b/tests/testthat/test-zero_crossings.R
@@ -0,0 +1,9 @@
+test_that("zero_crossings", {
+  x <- sin(seq(0, 4 * pi, length.out = 100))
+  out <- zero_crossings(x)
+  expect_equal(out, c(1, 25.74975, 50.5, 75.25025), tolerance = 1e-4)
+  out <- find_inversions(x)
+  expect_equal(out, c(12.87478, 37.62484, 62.37516, 87.12522), tolerance = 1e-4)
+  expect_true(is.na(zero_crossings(c(1, 2))))
+  excpect_error(zero_crossings(1), regex = "is not smaller")
+})