test: Add E2E test for RHINO_NPM env var

.github/workflows/e2e-test.yml

@@ -65,6 +65,12 @@ jobs:
           cd RhinoApp
           Rscript ../test-dependencies.R
 
+      - name: Node.js commands should respect RHINO_NPM
+        if: always()
+        run: |
+          cd RhinoApp
+          Rscript ../test-custom-npm.R
+
       - name: lint_r() should detect lint errors in R scripts
         if: always()
         run: |

tests/e2e/test-custom-npm.R

@@ -0,0 +1,22 @@
+local({
+  tmp <- withr::local_tempdir()
+  wrapper_path <- fs::path(tmp, "wrapper")
+  touch_path <- fs::path(tmp, "it_works")
+
+  # Prepare a wrapper script which creates an "it_works" file and runs npm.
+  fs::file_create(wrapper_path, mode = "u=rwx")
+  writeLines(
+    c(
+      '#!/bin/sh',
+      paste('touch', touch_path),
+      'exec npm "$@"'
+    ),
+    wrapper_path
+  )
+
+  # Use the wrapper script instead of npm.
+  withr::local_envvar(RHINO_NPM = wrapper_path)
+  rhino:::npm("--version")
+
+  testthat::expect_true(fs::file_exists(touch_path))
+})