--- a
+++ b/tests/integration/tables/test_emis.py
@@ -0,0 +1,97 @@
+from datetime import date
+
+from ehrql import Dataset
+from ehrql.tables import emis
+
+
+def test_patients_age_on(in_memory_engine):
+    in_memory_engine.populate(
+        {
+            emis.patients: [
+                dict(patient_id=1, date_of_birth=date(1980, 1, 1)),
+                dict(patient_id=2, date_of_birth=date(1800, 1, 1)),
+                dict(patient_id=3, date_of_birth=date(2010, 1, 1)),
+                dict(patient_id=4, date_of_birth=date(2010, 1, 2)),
+            ]
+        }
+    )
+
+    dataset = Dataset()
+    dataset.define_population(emis.patients.exists_for_patient())
+    dataset.age_2010 = emis.patients.age_on("2010-01-01")
+    results = in_memory_engine.extract(dataset)
+
+    assert results == [
+        {"patient_id": 1, "age_2010": 30},
+        {"patient_id": 2, "age_2010": 210},
+        {"patient_id": 3, "age_2010": 0},
+        {"patient_id": 4, "age_2010": -1},
+    ]
+
+
+def test_practice_registrations_spanning(
+    in_memory_engine,
+):
+    in_memory_engine.populate(
+        # Registrations before time period
+        {
+            emis.patients: [
+                dict(
+                    patient_id="1",
+                    registration_start_date=date(2000, 1, 1),
+                    registration_end_date=date(2005, 1, 1),
+                ),
+            ]
+        },
+        # Registration from before time period, and with NULL end date
+        {
+            emis.patients: [
+                dict(
+                    patient_id="2",
+                    registration_start_date=date(2000, 1, 1),
+                    registration_end_date=None,
+                ),
+            ]
+        },
+        # Registration with end date after time period ends
+        {
+            emis.patients: [
+                dict(
+                    patient_id="3",
+                    registration_start_date=date(2000, 1, 1),
+                    registration_end_date=date(2020, 1, 1),
+                ),
+            ]
+        },
+        # Registration with start date after time period starts
+        {
+            emis.patients: [
+                dict(
+                    patient_id="4",
+                    registration_start_date=date(2010, 2, 1),
+                    registration_end_date=date(2020, 1, 1),
+                ),
+            ]
+        },
+        # Registration with start date and end date inside time period
+        {
+            emis.patients: [
+                dict(
+                    patient_id="5",
+                    registration_start_date=date(2010, 2, 1),
+                    registration_end_date=date(2010, 12, 1),
+                ),
+            ]
+        },
+    )
+
+    dataset = Dataset()
+    dataset.define_population(
+        emis.patients.has_practice_registration_spanning("2010-01-01", "2011-01-01")
+    )
+    results = in_memory_engine.extract(dataset)
+
+    assert results == [
+        {"patient_id": "2"},
+        {"patient_id": "3"},
+    ]