diff --git a/tests/testthat/test-angle-difference.R b/tests/testthat/test-angle-difference.R
new file mode 100644
index 0000000..edbf0b4
--- /dev/null
+++ b/tests/testthat/test-angle-difference.R
@@ -0,0 +1,19 @@
+test_that("angle difference uses sum for opposite-sign bearings (#8)", {
+  # ComputeError: when gammaM and gammaC have opposite signs the delta
+  # is |gammaC + gammaM| instead of |gammaC - gammaM|, so that bearings
+  # straddling the +/-pi discontinuity yield a small angular difference.
+  gammaM <- -3.0
+  gammaC <- 2.8
+  expect_true(gammaM < 0 && gammaC > 0)
+  expect_equal(abs(gammaC + gammaM), 0.2)
+  expect_lt(abs(gammaC + gammaM), abs(gammaC - gammaM))
+})
+
+test_that("recmap on a shuffled checkerboard keeps small relpos errors", {
+  set.seed(1)
+  res <- sapply(1:10, function(i) {
+    cm <- recmap(checkerboard(8)[sample(64, 64), ])
+    mean(cm$relpos.error)
+  })
+  expect_true(all(res < 1))
+})