--- a
+++ b/tests/integration/backends/conftest.py
@@ -0,0 +1,51 @@
+import pytest
+import sqlalchemy
+
+from ehrql.backends.emis import EMISBackend
+from ehrql.backends.tpp import TPPBackend
+
+
+def _get_select_all_query(request, backend):
+    try:
+        ql_table = request.function._table
+    except AttributeError:  # pragma: no cover
+        raise RuntimeError(
+            f"Function '{request.function.__name__}' needs the "
+            f"`@register_test_for(table)` decorator applied"
+        )
+
+    qm_table = ql_table._qm_node
+    sql_table = backend.get_table_expression(qm_table.name, qm_table.schema)
+    columns = [
+        # Using `type_coerce(..., None)` like this strips the type information from the
+        # SQLAlchemy column meaning we get back the type that the column actually is in
+        # database, not the type we've told SQLAlchemy it is.
+        sqlalchemy.type_coerce(column, None).label(column.key)
+        for column in sql_table.columns
+    ]
+    return sqlalchemy.select(*columns)
+
+
+def _select_all_fn(select_all_query, database):
+    def _select_all(*input_data):
+        database.setup(*input_data)
+        with database.engine().connect() as connection:
+            results = connection.execute(select_all_query)
+            return sorted(
+                [row._asdict() for row in results], key=lambda x: x["patient_id"]
+            )
+
+    return _select_all
+
+
+@pytest.fixture
+def select_all_emis(request, trino_database):
+    select_all_query = _get_select_all_query(request, EMISBackend())
+    return _select_all_fn(select_all_query, trino_database)
+
+
+@pytest.fixture
+def select_all_tpp(request, mssql_database):
+    backend = TPPBackend(config={"TEMP_DATABASE_NAME": "temp_tables"})
+    select_all_query = _get_select_all_query(request, backend)
+    return _select_all_fn(select_all_query, mssql_database)