docs: explain how to run tests locally (#17783)

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This PR explains that we use`vdev` for testing and gives instructions
for using vdev to run tests locally.

Author: DominicBurkart

CONTRIBUTING.md

@@ -24,6 +24,7 @@ Vector team member will find this document useful.
       - [Daily tests](#daily-tests)
     - [Flakey tests](#flakey-tests)
       - [Test harness](#test-harness)
+  - [Running Tests Locally](#running-tests-locally)
   - [Deprecations](#deprecations)
   - [Dependencies](#dependencies)
 - [Next steps](#next-steps)
@@ -210,6 +211,17 @@ any pull request with:
 /test -t <name>
 ```
 
+### Running Tests Locally
+
+To run tests locally, use [cargo vdev](https://github.com/vectordotdev/vector/blob/master/vdev/README.md).
+
+Unit tests can be run by calling `cargo vdev test`.
+
+Integration tests are not run by default when running
+`cargo vdev test`. Instead, they are accessible via the integration subcommand (example:
+`cargo vdev int test aws` runs aws-related integration tests). You can find the list of available integration tests using `cargo vdev int show`. Integration tests require docker or podman to run.
+
+
 ### Deprecations
 
 When deprecating functionality in Vector, see [DEPRECATION.md](DEPRECATION.md).

vdev/README.md

@@ -11,6 +11,7 @@ Table of Contents:
   - [Repository](#repository)
   - [Starship](#starship)
 - [CLI](#cli)
+- [Running Tests](#running-tests)
 
 ## Installation
 
@@ -65,3 +66,10 @@ when = true
 The CLI uses [Clap](https://github.com/clap-rs/clap) with the `derive` construction mechanism and is stored in the [commands](src/commands) directory.
 
 Every command group/namespace has its own directory with a `cli` module, including the root `vdev` command group. All commands have an `exec` method that provides the actual implementation, which in the case of command groups will be calling sub-commands.
+
+
+## Running Tests
+
+Unit tests can be run by calling `cargo vdev test`.
+
+Integration tests are not run by default when running`cargo vdev test`. Instead, they are accessible via the integration subcommand (example: `cargo vdev int test aws` runs aws-related integration tests). You can find the list of available integration tests using `cargo vdev int show`. Integration tests require docker or podman to run.