added fix for tests

backend/Tests/AbsenceTest.cs

@@ -1,5 +1,6 @@
 using Api.StaffingController;
 using Core.Absences;
+using Core.Agreements;
 using Core.Consultants;
 using Core.Customers;
 using Core.DomainModels;
@@ -56,16 +57,39 @@ public void AvailabilityCalculation(
             Consultants = Substitute.For<List<Consultant>>()
         };
 
+        var customer = new Customer
+        {
+            Id = 1,
+            Name = "TestCustomer",
+            Organization = org,
+            Projects = new List<Engagement>()
+        };
+
+        var engagement = new Engagement
+        {
+            Id = 1,
+            Customer = customer,
+            State = EngagementState.Order,
+            IsBillable = true,
+            Staffings = new List<Staffing>(),
+            Name = "TestProject",
+
+        };
+
+        customer.Projects.Add(engagement);
 
         Consultant consultant = new()
         {
             Id = 1,
             Name = "Test Variant",
             Email = "[email protected]",
             GraduationYear = 2010,
-            Department = department
+            Department = department,
+            Projects = new List<Engagement>()
         };
 
+        consultant.Projects.Add(engagement);
+
         var mondayDateOnly = numberOfHolidays switch
         {
             0 => new DateOnly(2023, 9, 4), // Week 36, 4th Sept 2023, (no public holidays)
@@ -76,12 +100,17 @@ public void AvailabilityCalculation(
         };
 
         var week = Week.FromDateOnly(mondayDateOnly);
-        var project = Substitute.For<Engagement>();
-        var customer = Substitute.For<Customer>();
-        customer.Name = "TestCustomer";
-        project.Customer = customer;
-        project.State = EngagementState.Order;
-        project.IsBillable = true;
+
+
+
+        Agreement agreement = new()
+        {
+            Id = 1,
+            EndDate = new DateTime(2023, 12, 31),
+            StartDate = new DateTime(2023, 1, 1),
+            EngagementId = 1,
+            Engagement = engagement,
+        };
 
 
         // TODO: Change this to update consultant data
@@ -108,11 +137,11 @@ public void AvailabilityCalculation(
         if (staffedHours > 0)
             consultant.Staffings.Add(new Staffing
             {
-                Engagement = project,
+                Engagement = engagement,
                 Consultant = consultant,
                 Hours = staffedHours,
                 Week = week,
-                EngagementId = project.Id,
+                EngagementId = engagement.Id,
                 ConsultantId = consultant.Id
             });
 
@@ -162,9 +191,12 @@ public void MultiplePlannedAbsences()
             Name = "Test Variant",
             Email = "[email protected]",
             GraduationYear = 2010,
-            Department = department
+            Department = department,
+            Projects = new List<Engagement>()
         };
 
+        consultant.Projects.Add(Substitute.For<Engagement>());
+
         var week = new Week(2000, 1);
 
         consultant.PlannedAbsences.Add(new PlannedAbsence