Run Tests for kubernetes/client-go Codebase

This document provides a step-by-step guide on how to run tests for the Kubernetes/client-go project using Go’s testing capabilities.

Prerequisites

Go Environment: Ensure that you have Go installed and properly configured on your system. You can verify your Go installation by running:
```
go version
```
Clone the Repository: Clone the Kubernetes/client-go repository if you haven’t done so already:
```
git clone https://github.com/kubernetes/client-go.git
cd client-go
```

Running Tests

Test Structure

The Kubernetes/client-go tests are structured as follows:

Unit tests are located alongside the code they test.
Integration tests can be found within specific package directories.
Examples using the fake client exist in the /examples directory.

Step-by-step Guide

Running All Tests: To run all tests in the project, execute the following command within the root of the repository:
```
go test ./...
```
This command compiles and runs tests in all subdirectories.
Running Tests with Verbose Output: If you desire verbose output during the test execution, you can add the -v flag:
```
go test -v ./...
```
Running Specific Tests: If you are targeting specific tests, you can navigate to that directory and execute:
```
go test -v ./subdirectory
```

Using the Fake Client in Tests: The project provides functionality for testing with a fake client. To run tests that specifically utilize the fake client, navigate to the examples/fake-client directory and run:

go test -v k8s.io/client-go/examples/fake-client

This demonstrates how to use a fake client with SharedInformerFactory in tests. Here is a brief code example that illustrates the creation and use of the fake client:

package fakeclient

import (
    "k8s.io/client-go/tools/cache"
    "k8s.io/client-go/kubernetes/fake"
)

func ExampleFakeClient() {
    // Create a fake client
    client := fake.NewSimpleClientset()

    // Set up informers
    informers := cache.NewSharedInformerFactory(client, 0)
    // Further examples of injecting events into those informers would follow.
}

Test Example: Here is an example of a unit test from the rest package:

package rest

import (
    "testing"
    "github.com/stretchr/testify/assert"
)

func TestBuildUserAgent(t *testing.T) {
    assert.New(t).Equal(
        "lynx/nicest (beos/itanium) kubernetes/baaaaaaaaad",
        buildUserAgent(
            "lynx", "nicest",
            "beos", "itanium", "baaaaaaaaad"))
}

Using the Test Main Function: Some tests may require a main test function for setup or teardown. For instance:
```
package main

import (
    "os"
    "testing"
)

func TestMain(m *testing.M) {
    os.Exit(m.Run())
}
```

Running Tests for Specific Components

If you want to run tests for specific packages such as the metadata tests containing fake resources, navigate to the package and launch the tests:
```
go test -v k8s.io/client-go/metadata/fake
```

The constants defined within the tests can also be referenced within individual test cases for clarity in verifying resource properties.

Conclusion

Running tests in the Kubernetes/client-go project is straightforward and leverages Go’s standard testing tools. Use the instructions provided above to find and run the tests that fit your development and testing needs.

The examples outlined here demonstrate how to effectively test using fake clients and other standard testing methodologies in a Go context.

Sources:

examples/README.md
examples/fake-client/README.md
rest/config_test.go
tools/cache/main_test.go
metadata/fake/simple_test.go