PermissionSet ps = [SELECT Id FROM PermissionSet WHERE Name = 'Account_Product__c'];

    PermissionSetAssignment psa = new PermissionSetAssignment();
    psa.AssigneeId = userList[0].Id;
    psa.PermissionSetId = ps.Id;
    insert psa;

    System.runAs(userList[0])
    {
        Account acc = AceTestData.createAccount();
        Product__c [] prodList = new Product__c[]{};
        prodList.add(new Product__c(Name='Test1', Category__c='Item1', Sub_Category__c='Item2'));
        prodList.add(new Product__c(Name='Test2', Category__c='Item3', Sub_Category__c='Item4'));
        insert prodList;

        Account_Product__c acp = new Account_Product__c(Account__c = acc.Id, Product__c = prodList[0].Id);
        insert acp;
        List<String> listS = new List<String>{};
        listS.add(prodList[0].Id);
        listS.add(prodList[1].Id);

        Account_Product__c[] testResult = DealAccountProductRevenueController.getAccountProducts(acc.Id, listS);
        System.assertEquals(testResult.size(), 2);
        System.assertEquals(testResult[0].Id, acp.Id);
    }