Minify-replace does not work when the vars are declared.

.eslintrc.js

@@ -72,6 +72,8 @@ module.exports = {
     ...getExperimentGlobals(),
     'IS_ESM': 'readonly',
     'IS_SXG': 'readonly',
+    'IS_MINIFIED': 'readonly',
+    'IS_FORTESTING': 'readonly',
     'AMP': 'readonly',
     'context': 'readonly',
     'global': 'readonly',

build-system/test-configs/forbidden-terms.js

@@ -148,11 +148,9 @@ const forbiddenTermsGlobal = {
   },
   '(?:var|let|const) +IS_FORTESTING +=': {
     message: 'IS_FORTESTING local var only allowed in mode.js.',
-    allowlist: ['src/core/mode/for-testing.js'],
   },
   '(?:var|let|const) +IS_MINIFIED +=': {
     message: 'IS_MINIFIED local var only allowed in core/mode/minified.js',
-    allowlist: ['src/core/mode/minified.js'],
   },
   '\\.prefetch\\(': {
     message: 'Do not use preconnect.prefetch, use preconnect.preload instead.',

src/core/mode/for-testing.js

@@ -14,14 +14,11 @@
  * limitations under the License.
  */
 
-// Magic constant that is replaced by babel.
-// IS_FORTESTING is only replaced when `amp dist` is called without the
-// --fortesting flag.
-const IS_FORTESTING = true;
-
 /**
- * Returns true whenever closure compiler is used with --fortesting. Calls are
- * DCE'd when compiled.
+ * Returns true whenever --fortesting is used.
+ * This is a magic constant replaced by babel.
+ *
+ * Calls are DCE'd when compiled.
  * @return {boolean}
  */
 export function isFortesting() {

src/core/mode/minified.js

@@ -14,12 +14,10 @@
  * limitations under the License.
  */
 
-// Magic constant that is replaced by babel.
-// IS_MINIFIED is always replaced with true when closure compiler is used
-const IS_MINIFIED = false;
-
 /**
  * Returns true whenever closure compiler is used.
+ * This is a magic constant that is replaced by babel.
+ *
  * @return {boolean}
  */
 export function isMinified() {