Add an initial test for the array error metrics script

tests/testthat/test-array_error_metrics.R

@@ -0,0 +1,51 @@
+test_that(
+    ".add_error_metrics",
+    {
+        if (!exists("spe")) {
+            spe <- spatialLIBD::fetch_data(type = "visiumStitched_brain_spe")
+        }
+
+        #   Use the existing object's colData to define coords before and after
+        #   aligning to the nearest new array coordinates (as well as define the
+        #   distance between spot centroids in pixels)
+        coords_new = colData(spe) |>
+            cbind(spatialCoords(spe)) |>
+            as_tibble() |>
+            select(
+                array_row, array_col, key, pxl_col_in_fullres,
+                pxl_row_in_fullres, pxl_col_in_fullres_rounded,
+                pxl_row_in_fullres_rounded, capture_area,
+                array_row_original, array_col_original
+            ) |>
+            group_by(capture_area) |>
+            slice_head(n = 10) |>
+            ungroup()
+        coords = coords_new |>
+            select(-c(array_row, array_col)) |>
+            rename(
+                array_row = array_row_original, array_col = array_col_original
+            )
+        inter_spot_dist_px = 277.1524
+
+        coords_err = .add_error_metrics(coords, coords_new, inter_spot_dist_px)
+
+        #   Two error-metric columns should be added
+        expect_equal(
+            setdiff(colnames(coords_err), colnames(coords_new)),
+            c("euclidean_error", "shared_neighbors")
+        )
+
+        #   Euclidean error is contrained to be between 0 and (less than) 1 spot
+        expect_equal(
+            all((coords_err$euclidean_error >= 0) & (coords_err$euclidean_error < 1)),
+            TRUE
+        )
+
+        #   Shared neighbors must similarly be between 0 and 1 (it's a
+        #   proportion)
+        expect_equal(
+            all((coords_err$shared_neighbors >= 0) & (coords_err$shared_neighbors <= 1)),
+            TRUE
+        )
+    }
+)