test: move Testingcursor into separate class

Also adds more convenience functions: counting with a where
statement and a wrapper to execute_values().

test/python/conftest.py

@@ -1,12 +1,11 @@
-import importlib
 import itertools
 import sys
+import tempfile
 from pathlib import Path
 
 import psycopg2
 import psycopg2.extras
 import pytest
-import tempfile
 
 SRC_DIR = Path(__file__) / '..' / '..' / '..'
 
@@ -21,38 +20,7 @@ import nominatim.tokenizer.factory
 
 import dummy_tokenizer
 import mocks
-
-class _TestingCursor(psycopg2.extras.DictCursor):
-    """ Extension to the DictCursor class that provides execution
-        short-cuts that simplify writing assertions.
-    """
-
-    def scalar(self, sql, params=None):
-        """ Execute a query with a single return value and return this value.
-            Raises an assertion when not exactly one row is returned.
-        """
-        self.execute(sql, params)
-        assert self.rowcount == 1
-        return self.fetchone()[0]
-
-    def row_set(self, sql, params=None):
-        """ Execute a query and return the result as a set of tuples.
-        """
-        self.execute(sql, params)
-
-        return set((tuple(row) for row in self))
-
-    def table_exists(self, table):
-        """ Check that a table with the given name exists in the database.
-        """
-        num = self.scalar("""SELECT count(*) FROM pg_tables
-                             WHERE tablename = %s""", (table, ))
-        return num == 1
-
-    def table_rows(self, table):
-        """ Return the number of rows in the given table.
-        """
-        return self.scalar('SELECT count(*) FROM ' + table)
+from cursor import TestingCursor
 
 
 @pytest.fixture
@@ -70,7 +38,7 @@ def temp_db(monkeypatch):
 
     conn.close()
 
-    monkeypatch.setenv('NOMINATIM_DATABASE_DSN' , 'dbname=' + name)
+    monkeypatch.setenv('NOMINATIM_DATABASE_DSN', 'dbname=' + name)
 
     yield name
 
@@ -113,7 +81,7 @@ def temp_db_cursor(temp_db):
     """
     conn = psycopg2.connect('dbname=' + temp_db)
     conn.set_isolation_level(0)
-    with conn.cursor(cursor_factory=_TestingCursor) as cur:
+    with conn.cursor(cursor_factory=TestingCursor) as cur:
         yield cur
     conn.close()
 

test/python/cursor.py

@@ -0,0 +1,52 @@
+"""
+Specialised psycopg2 cursor with shortcut functions useful for testing.
+"""
+import psycopg2.extras
+
+class TestingCursor(psycopg2.extras.DictCursor):
+    """ Extension to the DictCursor class that provides execution
+        short-cuts that simplify writing assertions.
+    """
+
+    def scalar(self, sql, params=None):
+        """ Execute a query with a single return value and return this value.
+            Raises an assertion when not exactly one row is returned.
+        """
+        self.execute(sql, params)
+        assert self.rowcount == 1
+        return self.fetchone()[0]
+
+
+    def row_set(self, sql, params=None):
+        """ Execute a query and return the result as a set of tuples.
+            Fails when the SQL command returns duplicate rows.
+        """
+        self.execute(sql, params)
+
+        result = set((tuple(row) for row in self))
+        assert len(result) == self.rowcount
+
+        return result
+
+
+    def table_exists(self, table):
+        """ Check that a table with the given name exists in the database.
+        """
+        num = self.scalar("""SELECT count(*) FROM pg_tables
+                             WHERE tablename = %s""", (table, ))
+        return num == 1
+
+
+    def table_rows(self, table, where=None):
+        """ Return the number of rows in the given table.
+        """
+        if where is None:
+            return self.scalar('SELECT count(*) FROM ' + table)
+
+        return self.scalar('SELECT count(*) FROM {} WHERE {}'.format(table, where))
+
+
+    def execute_values(self, *args, **kwargs):
+        """ Execute the execute_values() function on the cursor.
+        """
+        psycopg2.extras.execute_values(self, *args, **kwargs)