Testing and Debugging @ docker/cli

Testing and Debugging

This outline explores the testing and debugging frameworks used for the Docker CLI.

Testing

The Docker CLI uses a comprehensive testing suite to ensure code quality and stability. It leverages three primary types of tests:

Unit tests: These tests focus on individual functions or components within the CLI. They aim to verify the correctness of individual code units in isolation.
Integration tests: These tests examine the interaction between different components of the CLI. They verify the seamless integration and cooperation between different code units.
End-to-end (E2E) tests: These tests simulate real-world scenarios by executing complete workflows and verifying the expected behavior of the CLI. They provide a holistic view of the CLI’s functionality and identify potential issues in the overall system.

The internal/test package provides various utilities and helpers for writing and running tests, including:

testutil.DockerCli: A utility function to create and run a Docker CLI client with custom configuration.
testutil.NewClient: A utility to create a new Docker client for testing purposes.
testutil.RequiresDaemon: A helper function to ensure the Docker daemon is available for integration tests.

Unit Tests

Unit tests are written using the go test framework and can be found in the internal/test package and within specific packages. They typically focus on verifying individual functions or components, such as parsing flags, validating inputs, or executing specific commands.

Example:

// Test the `docker version` command
          func TestVersion(t *testing.T) {
              // Create a new Docker client
              cli, err := testutil.NewClient()
              if err != nil {
                  t.Fatal(err)
              }
              // Run the `docker version` command
              output, err := cli.Version()
              if err != nil {
                  t.Fatal(err)
              }
              // Assert the output matches the expected format
              assert.Contains(t, output, "Docker version")
          }

Integration Tests

Integration tests are also written using the go test framework and often leverage the testutil package. These tests examine the interaction between different components within the CLI.

Example:

// Test the `docker run` command with a specific image
          func TestRunContainer(t *testing.T) {
              // Create a new Docker client
              cli, err := testutil.NewClient()
              if err != nil {
                  t.Fatal(err)
              }
              // Run the `docker run` command with a specific image
              output, err := cli.Run(context.Background(), "alpine", []string{"echo", "hello"})
              if err != nil {
                  t.Fatal(err)
              }
              // Assert the expected output is printed
              assert.Contains(t, output, "hello")
          }

End-to-End (E2E) Tests

E2E tests are located in the test/e2e directory. They simulate real-world scenarios by executing complete workflows and verifying the expected behavior of the CLI. These tests are designed to run on a dedicated test environment with a running Docker daemon.

Example:

// Test the `docker pull` and `docker run` commands
          func TestPullAndRun(t *testing.T) {
              // Run the `docker pull` command for a specific image
              output, err := docker.RunCommand([]string{"pull", "alpine:latest"}, t)
              if err != nil {
                  t.Fatalf("failed to pull image: %v", err)
              }
              // Check for expected output
              assert.Contains(t, output, "alpine:latest")
          
              // Run a container based on the pulled image
              output, err = docker.RunCommand([]string{"run", "--rm", "alpine", "echo", "hello"}, t)
              if err != nil {
                  t.Fatalf("failed to run container: %v", err)
              }
              // Check for expected output
              assert.Contains(t, output, "hello")
          }

Debugging

For debugging purposes, the Docker CLI offers several options:

Logging: The CLI uses standard Go logging facilities and can be configured to log various levels of detail.
Tracing: Tracing can be enabled to provide detailed information about the execution flow of the CLI.
Debugging tools: Standard Go debugging tools, such as go debug, can be used to inspect the code and identify issues.

Example:

To enable logging for debugging purposes, you can set the DEBUG environment variable to true. This will enable debug-level logging for all components. You can also set the DEBUG variable to a specific component name to enable debugging for that specific component.

DEBUG=true docker version

Additional Resources: