I'm writing a test suite for Django that runs tests in a tree-like fashion. For example, Testcase A might have 2 outcomes, and Testcase B might have 1, and Testcase C might have 3. The tree looks like this
X
/
A-B-C-X
\ \
B X
\ X
\ /
C-X
\
X
For each path in the tree above, the database contents may be different. So at each fork, I'm thinking of creating an in-memory copy of the current state of the database, and then feeding that parameter into the next test.
Anyone have an idea about how to essentially copy the in-memory database to another one, and then get a reference to pass that database around?
Thanks!
Alright, after a fun adventure I figured this one out.
from django.db import connections
import sqlite3
# Create a Django database connection for our test database
connections.databases['test'] = {'NAME': ":memory:", 'ENGINE': "django.db.backends.sqlite3"}
# We assume that the database under the source_wrapper hasn't been created
source_wrapper = connections['default'] # put alias of source db here
target_wrapper = connections['test']
# Create the tables for the source database
source_wrapper.creation.create_test_db()
# Dump the database into a single text query
query = "".join(line for line in source_wrapper.connection.iterdump())
# Generate an in-memory sqlite connection
target_wrapper.connection = sqlite3.connect(":memory:")
target_wrapper.connection.executescript(query)
And now the database called test
will be a carbon copy of the default
database. Use target_wrapper.connection as a reference to the newly created database.
Here is a function that copies databases. Both the source and destination can be in-memory or on-disk (the default destination is a copy in-memory):
import sqlite3
def copy_database(source_connection, dest_dbname=':memory:'):
'''Return a connection to a new copy of an existing database.
Raises an sqlite3.OperationalError if the destination already exists.
'''
script = ''.join(source_connection.iterdump())
dest_conn = sqlite3.connect(dest_dbname)
dest_conn.executescript(script)
return dest_conn
And here is an example of how it applies to your use case:
from contextlib import closing
with closing(sqlite3.connect('root_physical.db')) as on_disk_start:
in_mem_start = copy_database(on_disk_start)
a1 = testcase_a_outcome1(copy_database(in_mem_start))
a2 = testcase_a_outcome1(copy_database(in_mem_start))
a1b = test_case_b(a1)
a2b = test_case_b(a2)
a1bc1 = test_case_c_outcome1(copy_database(a1b))
a1bc2 = test_case_c_outcome2(copy_database(a1b))
a1bc3 = test_case_c_outcome3(copy_database(a1b))
a2bc1 = test_case_c_outcome1(copy_database(a2b))
a2bc2 = test_case_c_outcome2(copy_database(a2b))
a2bc3 = test_case_c_outcome3(copy_database(a2b))
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