test: unify falsy pattern handling in variable matcher

A falsy name, scope, or origin pattern now skips the find filter
uniformly, matching the absence assertions downstream; previously only
origin had the guard and null name/scope patterns could never match.

Related to camunda/camunda-modeler#5985

Author: barinali

test/assertions.js

@@ -2,10 +2,6 @@ const { expect } = require('chai');
 const { has } = require('min-dash');
 
 
-function isDefined(value) {
-  return typeof value !== 'undefined';
-}
-
 function findVariable(variables, expectedVariable) {
   const {
     name,
@@ -14,9 +10,9 @@ function findVariable(variables, expectedVariable) {
   } = expectedVariable;
 
   const variable = variables.find(
-    v => (!isDefined(name) || v.name === name)
-      && (!isDefined(scope) || v.scope?.id === scope)
-      && (!isDefined(origin) || !origin || matchesOrigin(v.origin, origin))
+    v => (!name || v.name === name)
+      && (!scope || v.scope?.id === scope)
+      && (!origin || matchesOrigin(v.origin, origin))
   );
 
   expect(variable, `variable[name=${name}, scope=${scope}]`).to.exist;