ref #26
ref #26

Changed to nill to kill mutants.
This is actually weird that the value of the parameter is not checked somewhere.

Mutants were:

```
Mutant configuration:
Matcher:         #<Mutant::Matcher::Config match_expressions: [SymptomCountFactory]>
Integration:     Mutant::Integration::Rspec
Jobs:            4
Includes:        []
Requires:        ["./config/environment"]
Subjects:        1
Mutations:       62
Results:         62
Kills:           59
Alive:           3
Runtime:         13.95s
Killtime:        36.79s
Overhead:        -62.09%
Mutations/s:     4.44
Coverage:        95.16%
Active subjects: 0
SymptomCountFactory.get_symptom:/mnt/d/tangu/Documents/UCL/cours/SINF2MS/Q4/Thesis/HAppi_backend/app/helper_factories/symptom_count_factory.rb:2
- rspec:73:./spec/helper_factories/symptom_count_factory_spec.rb:29/SymptomCountFactory.get_symptom with existing symptom_id, user_id whith all occurrences within the given interval returns the symptom with its id
- rspec:74:./spec/helper_factories/symptom_count_factory_spec.rb:33/SymptomCountFactory.get_symptom with existing symptom_id, user_id whith all occurrences within the given interval contains 6 occurrences
- rspec:75:./spec/helper_factories/symptom_count_factory_spec.rb:37/SymptomCountFactory.get_symptom with existing symptom_id, user_id whith all occurrences within the given interval contains occurrences with the correct user_id
- rspec:76:./spec/helper_factories/symptom_count_factory_spec.rb:48/SymptomCountFactory.get_symptom with existing symptom_id, user_id with no occurrences within the given interval raises an exception
- rspec:77:./spec/helper_factories/symptom_count_factory_spec.rb:57/SymptomCountFactory.get_symptom with existing symptom_id, user_id with 3 occurrences excluded because they are after end_date contains 3 occurrences
- rspec:78:./spec/helper_factories/symptom_count_factory_spec.rb:66/SymptomCountFactory.get_symptom with existing symptom_id, user_id with 3 occurrences excluded because they are before start_date contains 3 occurrences
evil:SymptomCountFactory.get_symptom:/mnt/d/tangu/Documents/UCL/cours/SINF2MS/Q4/Thesis/HAppi_backend/app/helper_factories/symptom_count_factory.rb:2:d7f48
@@ -1,4 +1,4 @@
 def self.get_symptom(symptom_id, user_id, start_date, end_date)
-  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(:occurrences).find(symptom_id)
+  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(nil).find(symptom_id)
 end
-----------------------
evil:SymptomCountFactory.get_symptom:/mnt/d/tangu/Documents/UCL/cours/SINF2MS/Q4/Thesis/HAppi_backend/app/helper_factories/symptom_count_factory.rb:2:8f57b
@@ -1,4 +1,4 @@
 def self.get_symptom(symptom_id, user_id, start_date, end_date)
-  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(:occurrences).find(symptom_id)
+  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(self).find(symptom_id)
 end
-----------------------
evil:SymptomCountFactory.get_symptom:/mnt/d/tangu/Documents/UCL/cours/SINF2MS/Q4/Thesis/HAppi_backend/app/helper_factories/symptom_count_factory.rb:2:7eb55
@@ -1,4 +1,4 @@
 def self.get_symptom(symptom_id, user_id, start_date, end_date)
-  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(:occurrences).find(symptom_id)
+  Symptom.includes(:occurrences).where("occurrences.user_id = :user_id AND occurrences.date BETWEEN :start_date AND :end_date", user_id: user_id, start_date: start_date, end_date: end_date).references(:occurrences__mutant__).find(symptom_id)
 end
 ```

 So we can clearly see that the tests still pass even when the value of the parameter of `references` is mutated

 Weird, really

GeoHealth/HAppi_backend,GeoHealth/HAppi_backend,GeoHealth/HAppi_backend,GeoHealth/HAppi_backend,GeoHealth/HAppi_backend