Cucumber test cases fail when run together but pass when run individually - cucumber

Question

I am using SpringBoot with Cucumber. One particular test case fails when run together and passes when run individually. Other Scenarios in the same feature file seems to work fine. I tried the following links but they did not work.
link1, link2, link3, link4, link5
I also tried to quarantine the problematic Scenario to a separate feature file and wrote an exclusive step def for the feature, but still no luck.
I tried introducing #After and #Before hooks to reset the value of Instance variable in stepdef file to null.
I even tried switching the position of Sample-payload and id Count Set
Now I ran out of options. Please help.
Feature File:
Scenario Outline: To check if the service returns all the ids when more than 10000 Ids are returned by the query
Given sample request <payload>
When the new end point is invoked
Then the service returns <idCount> Ids
Examples:
| payload | idCount |
| sample-payload-1 | 17575 |
| sample-payload-2 | 4 |
| sample-payload-3 | 23535 |
| sample-payload-4 | 34535 |
Step Def File:
public class MyStepdefs extends AbstractStepsDefs {
#Autowired
MyController myController;
private String requestPayload;
private List<String> ids;
#Given("^sample request (.+)$")
public void sample_request_something(String payload) throws Throwable {
this.requestPayload = payload;
}
#When("^the new end point is invoked$")
public void the_new_end_point_is_invoked() throws Throwable {
String responseJSON = MyUtil.getPostResponseJSON(myController, "/ids", requestPayload);
responseJSON = responseJSON.replace("[", "").replace("]", "").replaceAll("\"", "");
ids = Arrays.asList(responseJSON.split(","));
}
#Then("^service returns list of available (.+)$")
public void service_returns_list_of_available_something(String ids) throws Throwable {
List<String> list = Arrays.asList(ids.split(","));
Assert.assertTrue(this.ids.containsAll(list));
}
#Then("^the service returns (.+) ids$")
public void the_service_returns_ids(String idCount) throws Throwable {
System.out.println("Actual Size:" + this.ids.size());
System.out.println("Expected Size:" + Integer.parseInt(idCount));
Assert.assertEquals(this.ids.size(), Integer.parseInt(idCount));
}
#After
#Before
public void cleanUp() {
ids = null;
}
}
Now I have run out of options. Please help.
UPDATE1:
The second then block in the stepdef class fails. The sample-payload-1 and sample-payload-2 pass, but the other two fails. Even after changing the order of the sample-payloads the tests fail.
The error I get is an Assertion error as the size of the ids list is not same. But when I run the same test Individually I don't get this error as the size matches.

Answer 1

The issue was with the Instance variable I had used as a counter to loop through a logic that fires the query and extracts the result. The first test sample [sample-payload-1] will alone work fine as it has a fresh copy of the instance counter. The subsequent samples will have only the altered counter value.
This explains why the test cases passed when ran individually as there is not another test that would have used the altered counter.
FIX: The fix was to reset the counter back to 0 before I exit the implementation/service class so that the subsequent request will have a fresh counter
Lesson Learnt: Never rely on an instance variable if the scope of the enclosing Class is Singleton. The value will keep changing for every call to the method in the Class