throw an error when trying to dedupe in global modenlf/no-global-dedupe

PR-URL: https://github.com/npm/cli/pull/2716
Credit: @nlf
Close: #2716
Reviewed-by: @ljharb, @wraithgar

1 files changed, 15 insertions, 0 deletions

diff --git a/test/lib/dedupe.js b/test/lib/dedupe.js
index ff2d2be53..b14185525 100644
--- a/test/lib/dedupe.js
+++ b/test/lib/dedupe.js
@@ -1,6 +1,21 @@
 const { test } = require('tap')
 const requireInject = require('require-inject')
 
+test('should throw in global mode', (t) => {
+  const dedupe = requireInject('../../lib/dedupe.js', {
+    '../../lib/npm.js': {
+      flatOptions: {
+        global: true,
+      },
+    },
+  })
+
+  dedupe([], er => {
+    t.match(er, { code: 'EDEDUPEGLOBAL' }, 'throws EDEDUPEGLOBAL')
+    t.end()
+  })
+})
+
 test('should remove dupes using Arborist', (t) => {
   const dedupe = requireInject('../../lib/dedupe.js', {
     '../../lib/npm.js': {