README: Add section on running tests (#357)

* README: Add section on running tests

* Add more test help

Author: kyleconroy

README.md

@@ -438,6 +438,53 @@ sponsor](https://github.com/sponsors/kyleconroy) today.
 
 Sponsors receive priority support via the sqlc Slack organization.
 
+## Development
+
+### Building
+
+For local development, install `sqlc` under an alias. We suggest `sqlc-dev`.
+
+```
+go build -o ~/go/bin/sqlc-dev ./cmd/sqlc
+```
+
+### Running Tests
+
+To run the tests, include the `exp` tag. Without this tag, a few tests will
+fail. 
+
+```
+go test --tags=exp ./...
+```
+
+To run the tests in the examples folder, a running PostgreSQL instance is
+required. The tests use the following environment variables to connect to the
+database:
+
+```
+Variable     Default Value
+-------------------------
+PG_HOST      127.0.0.1
+PG_PORT      5432
+PG_USER      postgres
+PG_PASSWORD  mysecretpassword
+PG_DATABASE  dinotest
+```
+
+```
+go test --tags=examples,exp ./...
+```
+
+### Regenerate exepected test output
+
+If you need to update a large number of expexted test output in the
+`internal/endtoend/testdata` directory, run the `regenerate.sh` script.
+
+```
+cd internal/endtoend
+./regenerate.sh
+```
+
 ## Acknowledgements
 
 sqlc was inspired by [PugSQL](https://pugsql.org/) and