docs: initial update of integration test docs

docs/INTEGRATION_TESTS.md

@@ -1,62 +1,79 @@
 # Integration Tests
 
-To run our current integration test suite:
+## Running
 
-Running the integration tests requires several docker containers to be
-running.  You can start the containers with:
+To run all named integration tests:
 
 ```shell
-docker-compose up
+make test-integration
 ```
 
-To run only the integration tests use:
+To run all tests, including unit and integration tests:
 
 ```shell
-make test-integration
+go test -count 1 -race ./...
+```
+
+## Developing
+
+To run integration tests against a service the project uses
+[testcontainers][1]. The makes it very easy to create and cleanup
+container-based tests.
+
+The `testutil/container.go` has a `Container` type that wraps this project to
+easily create containers for testing in Telegraf. A typical test looks like
+the following:
+
+```go
+servicePort := "5432"
+
+container := testutil.Container{
+    Image:        "postgres:alpine",
+    ExposedPorts: []string{servicePort},
+    Env: map[string]string{
+        "POSTGRES_HOST_AUTH_METHOD": "trust",
+    },
+    WaitingFor: wait.ForAll(
+        wait.ForLog("database system is ready to accept connections"),
+        wait.ForListeningPort(nat.Port(servicePort)),
+    ),
+}
+
+err := container.Start()
+require.NoError(t, err, "failed to start container")
+
+defer func() {
+    require.NoError(t, container.Terminate(), "terminating container failed")
+}()
 ```
 
-Use `make docker-kill` to stop the containers.
-
-Contributing integration tests:
-
-- Add Integration to the end of the test name so it will be run with the above command.
-- Writes tests where no library is being used in the plugin
-- There is poor code coverage
-- It has dynamic code that only gets run at runtime eg: SQL
-
-Current areas we have integration tests:
-
-| Area                               | What it does                              |
-|------------------------------------|-------------------------------------------|
-| Inputs: Aerospike                  |                                           |
-| Inputs: Disque                     |                                           |
-| Inputs: Dovecot                    |                                           |
-| Inputs: Mcrouter                   |                                           |
-| Inputs: Memcached                  |                                           |
-| Inputs: Mysql                      |                                           |
-| Inputs: Opcua                      |                                           |
-| Inputs: Openldap                   |                                           |
-| Inputs: Pgbouncer                  |                                           |
-| Inputs: Postgresql                 |                                           |
-| Inputs: Postgresql extensible      |                                           |
-| Inputs: Procstat / Native windows  |                                           |
-| Inputs: Prometheus                 |                                           |
-| Inputs: Redis                      |                                           |
-| Inputs: Sqlserver                  |                                           |
-| Inputs: Win perf counters          |                                           |
-| Inputs: Win services               |                                           |
-| Inputs: Zookeeper                  |                                           |
-| Outputs: Cratedb / Postgres        |                                           |
-| Outputs: Elasticsearch             |                                           |
-| Outputs: Kafka                     |                                           |
-| Outputs: MQTT                      |                                           |
-| Outputs: Nats                      |                                           |
-| Outputs: NSQ                       |                                           |
-
-Areas we would benefit most from new integration tests:
-
-| Area                               |
-|------------------------------------|
-|  SNMP                              |
-|  MYSQL                             |
-|  SQLSERVER                         |
+The `servicePort` is the port the service is running on and Telegraf will
+connect to. When the port is specified as a single value (e.g. `11211`) then
+testcontainers will generate a random port for the service to start on. This
+way multiple tests can be run and prevent ports from conflicting.
+
+The `test.Container` type requires at least the following three items:
+
+1. An image name from [DockerHub][2], which can include a specific tag or not
+2. An array of port(s) to expose to the test to connect to
+3. A wait stanza. This lays out what testcontainers will wait for to determine
+  that the container has started and is ready for use by the test. It is best
+  to provide not only a port, but also a log message. Ports can come up very
+  early in the container, and the service may not be ready.
+
+There are other optional parameters like `Env` to pass environmental variables
+to the container or `BindMounts` to pass test data into the container as well.
+
+User's should start the container and then defer termination of the container.
+
+[1]: <https://golang.testcontainers.org/> "testcontainers-go"
+[2]: <https://hub.docker.com/> "DockerHub"
+
+## Contributing
+
+When adding integrations tests please do the following:
+
+- Add integration to the end of the test name
+- Use testcontainers when an external service is required
+- Use the testutil.Container to setup and configure testcontainers
+- Ensure the testcontainer wait stanza is well-tested