Added new testing documentation (#3823)

* Added new testing documentation

Signed-off-by: Derek Nola <derek.nola@suse.com>

CONTRIBUTING.md

@@ -10,6 +10,8 @@ If you're interested in contributing documentation, please note the following:
 - Doc issues are raised in this repository, and they are tracked under the `kind/documentation` label.
 - Pull requests are submitted to the K3s documentation source in the [Rancher docs repository.](https://github.com/rancher/docs/) The K3s docs content is in the `content/k3s/` directory.
 
+If you're interested in contributing new tests, please see the `TESTING.md` in the tests directory.
+
 ## Pull request and git commit guidance
 
 ### Opening PRs and organizing commits

tests/TESTING.md

@@ -0,0 +1,103 @@
+# Testing Standards in K3s
+
+Go testing in K3s comes in 3 forms: Unit, Integration, and End-to-End (E2E). This
+document will explain *when* each test should be written and *how* each test should be
+generated, formatted, and run.
+
+Note: all shell commands given are relateive to the root k3s repo directory.
+___
+
+## Unit Tests
+
+Unit tests should be written when a component or function of a package needs testing.
+Unit tests should be used for "white box" testing.
+
+### Framework
+
+All unit tests in K3s follow a [Table Driven Test](https://github.com/golang/go/wiki/TableDrivenTests) style. Specifically, K3s unit tests are automatically generated using the [gotests](https://github.com/cweill/gotests) tool. This is built into the Go vscode extension, has documented integrations for other popular editors, or can be run via command line. Additionally, a set of custom templates are provided to extend the generated test's functionality. To use these templates, call:
+
+```bash
+gotests --template_dir=<PATH_TO_K3S>/contrib/gotests_templates
+```
+
+Or in vscode, edit the Go extension setting `Go: Generate Tests Flags`  
+and add `--template_dir=<PATH_TO_K3S>/contrib/gotests_templates` as an item.
+
+To facilitate unit test creation, see `tests/util/runtime.go` helper functions.
+
+### Format
+
+All unit tests should be placed within the package of the file they test.  
+All unit test files should be named: `<FILE_UNDER_TEST>_test.go`.  
+All unit test functions should be named: `Test_Unit<FUNCTION_TO_TEST>` or `Test_Unit<RECEIVER>_<METHOD_TO_TEST>`.  
+See the [etcd unit test](https://github.com/k3s-io/k3s/blob/master/pkg/etcd/etcd_test.go) as an example.
+
+### Running
+
+```bash
+go test ./pkg/... -run Unit
+```
+
+Note: As unit tests call functions directly, they are the primary drivers of K3s's code coverage
+metric.
+
+___
+
+## Integration Tests
+
+Integration tests should be used to test a specific functionality of k3s that exists across multiple Go packages, either via exported function calls, or more often, CLI comands.
+Integration tests should be used for "black box" testing. 
+
+### Framework
+
+All integration tests in K3s follow a [Behavior Diven Development (BDD)](https://en.wikipedia.org/wiki/Behavior-driven_development) style. Specifically, K3s uses [Ginkgo](https://onsi.github.io/ginkgo/) and [Gomega](https://onsi.github.io/gomega/) to drive the tests.  
+To generate an initial test, the command `ginkgo bootstrap` can be used.
+
+To facilitate K3s CLI testing, see `tests/util/cmd.go` helper functions.
+
+### Format
+
+Integration tests can be placed in two areas:  
+
+1. Next to the go package they intend to test.
+2. In `tests/integration/` for package agnostic testing.  
+
+Package specific integration tests should use the `<PACKAGE_UNDER_TEST>_test` package.  
+Package agnostic integration tests should use the `integration` package.  
+All integration test files should be named: `<TEST_NAME>_int_test.go`  
+All integration test functions should be named: `Test_Integration<Test_Name>`.  
+See the [etcd snapshot test](https://github.com/k3s-io/k3s/blob/master/pkg/etcd/etcd_int_test.go) as a package specific example.  
+See the [local storage test](https://github.com/k3s-io/k3s/blob/master/tests/integration/localstorage_int_test.go) as a package agnostic example.
+
+### Running
+
+```bash
+go test ./pkg/... ./tests/... -run Integration
+```
+
+___
+
+## End-to-End (E2E) Tests
+
+End-to-end tests utilize [Ginkgo](https://onsi.github.io/ginkgo/) and [Gomega](https://onsi.github.io/gomega/) like the integration tests, but rely on separate testing utilities and are self-contained within the `test/e2e` directory. E2E tests cover complete K3s single and multi-cluster configuration and administration: bringup, update, teardown etc.  
+E2E tests are run nightly as part of K3s quality assurance (QA).
+
+### Format
+
+All E2E tests should be placed under the `e2e` package.  
+All E2E test functions should be named: `Test_E2E<TEST_NAME>`.  
+See the [upgrade cluster test](https://github.com/k3s-io/k3s/blob/master/tests/e2e/upgradecluster_test.go) as an example.
+
+### Running
+
+Generally, E2E tests are run as a nightly Jenkins job for QA. They can still be run locally but additional setup may be required.
+
+```bash
+go test ./tests/... -run E2E
+```
+
+## Contributing New Or Updated Tests
+
+___
+We gladly accept new and updated tests of all types. If you wish to create
+a new test or update an existing test, please submit a PR with a title that includes the words `<NAME_OF_TEST> (Created/Updated)`.