diff --git a/output/timetable.js b/output/timetable.js
index ec74399..a3a1121 100644
--- a/output/timetable.js
+++ b/output/timetable.js
@@ -361,6 +361,7 @@ function viewWorker(worker) {
     dlg = $(`<div class='dialog' title='${ds.worker}'>
     Site: ${ds.site}</br>
     FTE: ${ds.fte} (${ds.fte_adj})</br>
+    Start date: ${ds.start_date}</br>
     End date: ${ds.end_date}</br>
     Non working days: ${ds.nwds}
     </div>`)
diff --git a/rota/run2.py b/rota/run2.py
index f4559ce..644a7e6 100644
--- a/rota/run2.py
+++ b/rota/run2.py
@@ -5,15 +5,7 @@ from workers import Worker
 
 from copy import deepcopy
 
-import math
-
-import scipy.stats as stats
-
-import statistics
-
 import datetime
-import itertools
-import operator
 
 use_neos = False
 
diff --git a/rota/shifts.py b/rota/shifts.py
index d291115..b2e2917 100644
--- a/rota/shifts.py
+++ b/rota/shifts.py
@@ -267,12 +267,13 @@ class RotaBuilder(object):
         if not results.solver.status:
             sys.exit(0)
 
-    def build_and_solve(self, options={"ratio": 0.1, "seconds": 1000, "threads": 10}):
+    def build_and_solve(self, options={"ratio": 0.1, "seconds": 1000, "threads": 10}, solve=True):
         self.build_shifts()
         self.build_workers()
         self.build_model()
 
-        self.solve_model(options=options)
+        if solve:
+            self.solve_model(options=options)
 
     def build_model(self):
         # Initialize model
@@ -1916,7 +1917,7 @@ class RotaBuilder(object):
         self.workers.append(worker)
 
     def add_workers(self, workers: List) -> None:
-        """Add multiple worker to the rota
+        """Add multiple workers to the rota
 
         Args:
             workers (List(Worker)):
@@ -1932,6 +1933,21 @@ class RotaBuilder(object):
         if not self.workers:
             raise NoWorkers("Workers must be added prior to calling build_workers")
 
+        self.workers_id_map = {}
+        self.workers_name_map = {}
+
+        for worker in self.workers:
+            wid = worker.id
+            if wid in self.workers_id_map:
+                raise ValueError(f"Worker with id '{wid}' has been added twice")
+            self.workers_id_map[wid] = worker
+
+            if worker.name in self.workers_name_map:
+                raise ValueError(f"Worker with name '{worker.name}' has been added twice")
+            self.workers_name_map[worker.name] = worker
+
+
+
         self.workers = sorted(self.workers)
 
         self.full_time_equivalent = sum(w.fte_adj for w in self.workers)
@@ -2216,6 +2232,9 @@ class RotaBuilder(object):
         s.extend(self.shifts_to_force_as_blocks())
         return s
 
+    def get_worker_by_name(self, name: str) -> Worker:
+        return self.workers_name_map[name]
+
     def get_workers_by_group(self) -> Dict[str, Worker]:
         group_workers = defaultdict(set)
         for worker in self.workers:
@@ -2315,6 +2334,7 @@ class RotaBuilder(object):
                         week_table[week][day][shift].append(worker.get_details())
         return week_table
 
+
     def get_worker_timetable(self):
         works = self.model.works
         timetable = {
@@ -2511,7 +2531,9 @@ class RotaBuilder(object):
 
             worker_td = """<td title='Site: {site}' class='worker {site}' 
             data-nwds='{nwds}' data-site='{site}' data-worker='{name}' 
-            data-fte='{fte}' data-fte_adj='{fte_adj}' data-end_date='{end_date}' 
+            data-fte='{fte}' data-fte_adj='{fte_adj}' 
+            data-start_date='{start_date}' 
+            data-end_date='{end_date}' 
             data-worker-targets='{targets}' data-shift-counts='{worker_shift_counts}' 
             data-weekend-target='{weekend_target}' 
             data-remote-site='{remote_site}' 
@@ -2527,6 +2549,7 @@ class RotaBuilder(object):
                 name=worker.name,
                 fte=worker.fte,
                 fte_adj=worker.fte_adj,
+                start_date=worker.start_date,
                 end_date=worker.end_date,
                 targets=worker_targets,
                 worker_shift_counts=json.dumps(shift_count_dict),
@@ -2645,6 +2668,22 @@ class RotaBuilder(object):
 
         return timetable
 
+    def get_worker_shifts_by_date(self, worker: Worker) -> Dict:
+        shifts = {}
+
+        n = 0
+        for week, day in self.get_week_day_combinations():
+            d = self.start_date + datetime.timedelta(n)
+            n = n + 1
+
+            temp = ""
+            for shift in self.get_shift_names_by_week_day(week, day):
+                if self.model.works[worker.id, week, day, shift].value > 0:
+                    shifts[d]=shift
+
+        return shifts
+
+
     def get_worker_shift_list(self, worker: Worker) -> List:
         shifts = []
 
@@ -2660,6 +2699,12 @@ class RotaBuilder(object):
 
         return shifts
 
+    def get_worker_shift_list_string(self, worker: Worker) -> str:
+        shifts = self.get_worker_shift_list(worker)
+
+        # Convert shift to a string representation
+        return "".join([i if i != "" else "-" for i in shifts])
+
     def get_shift_summary(self):
         works = self.model.works
         timetable = {
diff --git a/rota/workers.py b/rota/workers.py
index e19770f..9110bac 100644
--- a/rota/workers.py
+++ b/rota/workers.py
@@ -2,10 +2,10 @@ import datetime
 from collections import defaultdict
 from typing import List
 
-#from .shifts import RotaBuilder, days, sites
+# from .shifts import RotaBuilder, days, sites
 import uuid
 
-#from rota.shifts import RotaBuilder
+# from rota.shifts import RotaBuilder
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
@@ -21,9 +21,10 @@ class Worker:
         grade: int,
         id=None,
         fte: int = 100,
-        nwd: list[str] | list[str, datetime.datetime, datetime.datetime]=[],
-        end_date: datetime.datetime | None =None,
-        oop=None,
+        nwd: list[str] | list[str, datetime.datetime, datetime.datetime] = [],
+        start_date: datetime.datetime | None = None,
+        end_date: datetime.datetime | None = None,
+        oop:list[(datetime.datetime, datetime.datetime, str)] | None = None,
         not_available_to_work=None,
         pref_not_to_work=None,
         work_requests=None,
@@ -57,57 +58,106 @@ class Worker:
 
         self.shift_target_number = defaultdict(int)
 
-        days_to_work = Rota.rota_days_length
+        #days_to_work = Rota.rota_days_length
+
+
+        # if no start date default to the start of the rota
+        if start_date is None:
+            self.start_date = Rota.start_date
+        else:
+            # ? test if start date is valid
+            self.start_date = start_date
 
         if end_date is None:
-            self.end_date = None
+            self.end_date = Rota.rota_end_date
         else:
-            self.end_date = datetime.datetime.strptime(end_date, "%d/%m/%y").date()
+            if isinstance(end_date, datetime.date):
+                self.end_date = end_date
+            else:
+                self.end_date = datetime.datetime.strptime(end_date, "%d/%m/%y").date()
 
             if self.end_date > Rota.rota_end_date:
                 self.end_date = Rota.rota_end_date
-            else:
-                if self.end_date > Rota.start_date:
-                    days_to_work = (self.end_date - Rota.start_date).days
 
-                    # add unavalabilities
-                    for weeks_days in Rota.weeks_days_product[days_to_work:]:
-                        week, day = weeks_days
-                        Rota.unavailable_to_work.add((self.id, week, day))
-                        Rota.unavailable_to_work_reason[
-                            (self.id, week, day)
-                        ] = "END DATE"
+            
+        #if self.start_date >= self.end_date:
+        #    raise ValueError("End date must be after start date")
+
+        days_to_work = (self.end_date - self.start_date).days
+
+        for week, day in Rota.weeks_days_product:
+            date = Rota.week_day_date_map[(week, day)]
+
+            if date < self.start_date:
+                Rota.unavailable_to_work.add((self.id, week, day))
+                Rota.unavailable_to_work_reason[
+                    (self.id, week, day)
+                ] = f"START DATE: {self.start_date}"
+
+            if date >= self.end_date: 
+                Rota.unavailable_to_work.add((self.id, week, day))
+                Rota.unavailable_to_work_reason[
+                    (self.id, week, day)
+                ] = f"END DATE: {self.end_date}"
+
+        #if self.start_date > Rota.start_date:
+        #    # add unavalabilities
+        #    for weeks_days in Rota.weeks_days_product[:days_to_work]:
+        #        week, day = weeks_days
+        #        Rota.unavailable_to_work.add((self.id, week, day))
+        #        Rota.unavailable_to_work_reason[
+        #            (self.id, week, day)
+        #        ] = f"START DATE: {self.start_date}"
+
+        #if self.end_date < Rota.rota_end_date:
+        #    # add unavalabilities
+        #    for weeks_days in Rota.weeks_days_product[days_to_work:]:
+        #        week, day = weeks_days
+        #        Rota.unavailable_to_work.add((self.id, week, day))
+        #        Rota.unavailable_to_work_reason[
+        #            (self.id, week, day)
+        #        ] = f"END DATE: {self.end_date}"
 
         if oop is not None:
-            start_oop, end_oop = oop
-            start_oop_date = datetime.datetime.strptime(start_oop, "%d/%m/%y").date()
-            end_oop_date = datetime.datetime.strptime(end_oop, "%d/%m/%y").date()
-
-            # ignore oops if they finish before the rota start date
-            print(end_oop_date, Rota.start_date)
-            if end_oop_date > Rota.start_date:
-                if start_oop_date > Rota.rota_end_date:
-                    pass
+            for start_oop, end_oop, oop_name in oop:
+                #start_oop, end_oop = oop
+                if isinstance(start_oop, datetime.date):
+                    start_oop_date = start_oop
                 else:
-                    if end_oop_date > Rota.rota_end_date:
-                        end_oop_date = Rota.rota_end_date
+                    start_oop_date = datetime.datetime.strptime(start_oop, "%d/%m/%y").date()
 
-                    if start_oop_date < Rota.start_date:
-                        start_oop_date = Rota.start_date
+                if isinstance(end_oop, datetime.date):
+                    end_oop_date = end_oop
+                else:
+                    end_oop_date = datetime.datetime.strptime(end_oop, "%d/%m/%y").date()
 
-                    oop_length = (end_oop_date - start_oop_date).days
-                    days_to_work = days_to_work - oop_length
+                if start_oop_date >= end_oop_date:
+                    raise ValueError("End OOP date must be after start date")
 
-                    days_until_oop = (start_oop_date - Rota.start_date).days
+                # ignore oops if they finish before the rota (or worker) start date
+                if end_oop_date > self.start_date:
+                    if start_oop_date > self.end_date:
+                        pass
+                    else:
+                        if end_oop_date > Rota.rota_end_date:
+                            end_oop_date = Rota.rota_end_date
 
-                    for weeks_days in Rota.weeks_days_product[
-                        days_until_oop : days_until_oop + oop_length
-                    ]:
-                        week, day = weeks_days
-                        Rota.unavailable_to_work.add((self.id, week, day))
-                        Rota.unavailable_to_work_reason[
-                            (self.id, week, day)
-                        ] = "OOP ()".format(oop)
+                        if start_oop_date < Rota.start_date:
+                            start_oop_date = Rota.start_date
+
+                        oop_length = (end_oop_date - start_oop_date).days
+                        days_to_work = days_to_work - oop_length
+
+                        days_until_oop = (start_oop_date - Rota.start_date).days
+
+                        for weeks_days in Rota.weeks_days_product[
+                            days_until_oop : days_until_oop + oop_length
+                        ]:
+                            week, day = weeks_days
+                            Rota.unavailable_to_work.add((self.id, week, day))
+                            Rota.unavailable_to_work_reason[
+                                (self.id, week, day)
+                            ] = f"OOP ({oop_name})".format(oop)
 
         if pref_not_to_work is not None:
             # loop throught dates converting to week / day combination
diff --git a/test/test_nwds.py b/test/test_nwds.py
index 35ac66e..f102cb5 100644
--- a/test/test_nwds.py
+++ b/test/test_nwds.py
@@ -1,5 +1,3 @@
-from copy import deepcopy
-from black import main
 import pytest
 from rota.shifts import NoWorkers, RotaBuilder, SingleShift, days
 
diff --git a/test/test_workers.py b/test/test_workers.py
new file mode 100644
index 0000000..0489f4a
--- /dev/null
+++ b/test/test_workers.py
@@ -0,0 +1,285 @@
+import pytest
+from rota.shifts import NoWorkers, RotaBuilder, SingleShift, days
+
+import datetime
+
+from rota.workers import Worker
+
+
+def setup_basic_rota():
+    weeks_to_rota = 10
+    start_date = datetime.date(2022, 3, 7)
+
+    return RotaBuilder(
+        start_date,
+        weeks_to_rota=weeks_to_rota,
+    )
+
+
+class TestWorkers:
+    def test_no_workers(self):
+        """Check error raised if attempt to solve with no workers"""
+        Rota = setup_basic_rota()
+
+        Rota.add_shifts(
+            SingleShift(
+                ("group1",),
+                "d",
+                12.5,
+                days[:5],
+                balance_offset=10,
+                workers_required=1,
+            ),
+            SingleShift(("group1",), "w", 12.5, days[5:], workers_required=1),
+        )
+
+        with pytest.raises(NoWorkers):
+            Rota.build_and_solve(solve=False)
+
+    def test_workers_duplicate_name(self):
+
+        Rota = setup_basic_rota()
+
+        workers = []
+        workers.append(Worker(Rota, "worker1", "group1", 1, fte=100))
+        workers.append(Worker(Rota, "worker1", "group1", 1, fte=100))
+        workers.append(Worker(Rota, "worker3", "group2", 1, fte=50))
+        workers.append(Worker(Rota, "worker4", "group2", 1, fte=50))
+
+        Rota.add_workers(workers)
+
+        Rota.add_shifts(
+            SingleShift(
+                ("group1",),
+                "d",
+                12.5,
+                days[:5],
+                balance_offset=10,
+                workers_required=1,
+            ),
+        )
+
+        with pytest.raises(ValueError):
+            Rota.build_and_solve(solve=False)
+
+    def test_worker_ftes(self):
+
+        weeks_to_rota = 10
+        start_date = datetime.date(2022, 3, 7)
+
+        Rota = RotaBuilder(
+            start_date,
+            weeks_to_rota=weeks_to_rota,
+        )
+
+        worker1_end_date = start_date + datetime.timedelta(weeks=weeks_to_rota / 2)
+
+        worker2_start_date = start_date + datetime.timedelta(weeks=weeks_to_rota / 2)
+
+        worker3_start_date = start_date + datetime.timedelta(weeks=weeks_to_rota / 4)
+        worker3_end_date = start_date + datetime.timedelta(weeks=3 * weeks_to_rota / 4)
+
+        workers = []
+        workers.append(
+            Worker(Rota, "worker1", "group1", 1, fte=100, end_date=worker1_end_date)
+        )
+        workers.append(
+            Worker(Rota, "worker2", "group1", 1, fte=100, start_date=worker2_start_date)
+        )
+        workers.append(
+            Worker(
+                Rota,
+                "worker3",
+                "group2",
+                1,
+                fte=100,
+                start_date=worker3_start_date,
+                end_date=worker3_end_date,
+            )
+        )
+        workers.append(Worker(Rota, "worker4", "group2", 1, fte=50))
+        workers.append(Worker(Rota, "worker5", "group2", 1, fte=50, nwd=["Mon", "Tue"]))
+        workers.append(
+            Worker(
+                Rota,
+                "worker6",
+                "group3",
+                1,
+                fte=100,
+                start_date=start_date + datetime.timedelta(weeks=weeks_to_rota),
+            )
+        )
+        workers.append(
+            Worker(Rota, "worker7", "group3", 1, fte=50, end_date=start_date)
+        )
+
+        Rota.add_workers(workers)
+
+        Rota.add_shifts(
+            SingleShift(
+                ("group1", "group2"),
+                "d",
+                12.5,
+                days[:5],
+                balance_offset=10,
+                workers_required=1,
+            ),
+        )
+
+        Rota.build_and_solve()
+
+        # All workers should have an adjusted fte of 50 %
+        for worker in Rota.get_workers():
+
+            if worker.site == "group3":
+                assert worker.fte_adj == 0
+                assert Rota.get_worker_shift_list(worker).count("d") == 0
+                continue
+
+            assert worker.fte_adj == 50
+
+            if worker.fte == 100:
+                assert worker.proportion_rota_to_work == 0.5
+                assert worker.days_to_work == 35
+
+            assert Rota.get_worker_shift_list(worker).count("d") == 10
+
+            if worker.name == "worker1":
+                assert Rota.get_worker_shift_list_string(worker).endswith("-"*(Rota.rota_days_length//2))
+            if worker.name == "worker2":
+                assert Rota.get_worker_shift_list_string(worker).startswith("-"*(Rota.rota_days_length//2))
+            if worker.name == "worker3":
+                assert Rota.get_worker_shift_list_string(worker).startswith("-"*(Rota.rota_days_length//4))
+                assert Rota.get_worker_shift_list_string(worker).endswith("-"*(Rota.rota_days_length//4))
+
+
+        assert Rota.results.solver.status == "ok"
+        assert Rota.results.solver.termination_condition == "optimal"
+
+        Rota.export_rota_to_html("worker_ftes")
+
+    def test_worker_oops(self):
+        weeks_to_rota = 10
+        start_date = datetime.date(2022, 3, 7)
+
+        Rota = RotaBuilder(
+            start_date,
+            weeks_to_rota=weeks_to_rota,
+        )
+
+        worker1_oop = [
+            (
+                start_date,
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2),
+                "First half OOP",
+            )
+        ]
+
+        worker2_oop = [
+            (
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2),
+                Rota.rota_end_date,
+                "First half OOP",
+            )
+        ]
+
+        worker3_start_date = start_date + datetime.timedelta(weeks=weeks_to_rota / 4)
+        worker3_oop = [
+            (
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2),
+                start_date + datetime.timedelta(weeks=3 * weeks_to_rota / 4),
+                "Quarter oop",
+            )
+        ]
+
+        worker4_oop = [
+            (
+                start_date,
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 4),
+                "Quarter oop",
+            ),
+            (
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2),
+                start_date
+                + datetime.timedelta(weeks=weeks_to_rota / 2)
+                + datetime.timedelta(weeks=weeks_to_rota / 4),
+                "Quarter oop 2",
+            ),
+        ]
+
+        workers = []
+        workers.append(Worker(Rota, "worker1", "group1", 1, fte=100, oop=worker1_oop))
+        workers.append(Worker(Rota, "worker2", "group1", 1, fte=100, oop=worker2_oop))
+        workers.append(
+            Worker(
+                Rota,
+                "worker3",
+                "group2",
+                1,
+                fte=100,
+                start_date=worker3_start_date,
+                oop=worker3_oop,
+            )
+        )
+        workers.append(Worker(Rota, "worker4", "group2", 1, oop=worker4_oop))
+        workers.append(Worker(Rota, "worker5", "group2", 1, fte=50, nwd=["Mon", "Tue"]))
+
+        worker6_oop = [
+            (
+                start_date,
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 6),
+                "oop",
+            ),
+            (
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2),
+                start_date + datetime.timedelta(weeks=weeks_to_rota / 2)
+                + datetime.timedelta(weeks=weeks_to_rota / 3),
+                " oop 2",
+            ),
+        ]
+
+        worker7_oop = [
+            (
+                start_date-datetime.timedelta(weeks=1),
+                Rota.rota_end_date,
+                "oop",
+            ),
+        ]
+
+
+        workers.append(Worker(Rota, "worker6", "group2", 1, fte=100, oop=worker6_oop))
+        workers.append(Worker(Rota, "worker7", "group3", 1, fte=100, oop=worker7_oop))
+
+        Rota.add_workers(workers)
+
+        Rota.add_shifts(
+            SingleShift(
+                ("group1", "group2"),
+                "d",
+                12.5,
+                days[:5],
+                balance_offset=10,
+                workers_required=1,
+            ),
+        )
+
+        Rota.build_and_solve()
+
+        # All workers should have an adjusted fte of 50 %
+        for worker in Rota.get_workers():
+            if worker.site == "group3":
+                assert worker.fte_adj == 0
+                continue
+
+            assert worker.fte_adj == pytest.approx(50, 2)
+
+            if worker.fte == 100:
+               assert worker.proportion_rota_to_work == pytest.approx(0.5, 0.2)
+               assert worker.days_to_work == pytest.approx(35, 1)
+
+            assert Rota.get_worker_shift_list(worker).count("d") in (8, 9)
+
+        assert Rota.results.solver.status == "ok"
+        assert Rota.results.solver.termination_condition == "optimal"
+
+        Rota.export_rota_to_html("worker_oops")