📝 Add an example of setting up a test database (#1144)

* Add an example of setting up a test database.

* 📝 Add/update docs for testing a DB with dependency overrides

* 🔧 Update test script, remove line removing test file as it is removed during testing

* ✅ Update testing coverage pragma

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

scripts/test.sh

@@ -3,10 +3,6 @@
 set -e
 set -x
 
-# Remove temporary DB
-if [ -f ./test.db ]; then
-    rm ./test.db
-fi
 bash ./scripts/lint.sh
 # Check README.md is up to date
 diff --brief docs/en/docs/index.md README.md