Generally you will want to include tests in the PR that implements the behaviour. In general I wouldn't approve PRs that don't include tests for the code being added.
If you want to scale down the size of your PRs (a great thing to do) you can cut back on the features being added in that PR. For example: Instead of a create and fetch API with no tests just create a PR with create and tests then follow up with a PR that includes fetch and tests.
Generally you will want to include tests in the PR that implements the behaviour. In general I wouldn't approve PRs that don't include tests for the code being added.
If you want to scale down the size of your PRs (a great thing to do) you can cut back on the features being added in that PR. For example: Instead of a create and fetch API with no tests just create a PR with create and tests then follow up with a PR that includes fetch and tests.