docs(ru): update testing.md (#1723)

Author: Alex-Sokolov

docs/ru/guide/testing.md

@@ -99,9 +99,7 @@ const testAction = (action, payload, state, expectedMutations, done) => {
 
     try {
       expect(type).to.equal(mutation.type);
-      if (payload) {
-        expect(payload).to.deep.equal(mutation.payload);
-      }
+      expect(payload).to.deep.equal(mutation.payload);
     } catch (error) {
       done(error);
     }