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Testing Linux Capability Control Implementation in Fluentd

This test suite validates the Linux capability control functionality in Fluentd, focusing on managing process capabilities through the CapCtl command-line interface. The tests ensure proper handling of capability operations like adding, dropping, clearing, and retrieving Linux capabilities.

Test Coverage Overview

The test suite provides comprehensive coverage of Fluentd’s capability control features:

Capability management operations (clear, add, drop, get)
File-based capability operations using temporary files
Error handling for invalid capabilities
Environment compatibility checks for Linux capabilities

Implementation Analysis

The testing approach utilizes Test::Unit framework with structured test cases organized into logical groups. It employs sub_test_cases to separate success scenarios, file-based operations, and invalid inputs. The implementation uses stdout capture to verify command output patterns and proper exception handling.

Technical Details

Key technical components include:

Test::Unit for test framework
Tempfile for temporary file handling
CapNG integration for Linux capability management
Regular expressions for output validation
Environment-specific test omission logic

Best Practices Demonstrated

The test suite exemplifies several testing best practices including proper test isolation, comprehensive error case coverage, and environment-aware testing. It demonstrates effective use of setup hooks, structured test organization, and clear test case naming conventions while maintaining focused test scenarios for each capability operation.

fluent/fluentd

test/command/test_cap_ctl.rb

            
require_relative '../helper'

require 'tempfile'
require 'fluent/command/cap_ctl'

class TestFluentCapCtl < Test::Unit::TestCase
  setup do
    omit "This environment does not handle Linux capability" unless defined?(CapNG)
  end

  sub_test_case "success" do
    test "clear capability" do
      logs = capture_stdout do
        Fluent::CapCtl.new(["--clear"]).call
      end
      expression = /\AClear capabilities .*\n/m
      assert_match expression, logs
    end

    test "add capability" do
      logs = capture_stdout do
        Fluent::CapCtl.new(["--add", "dac_override"]).call
      end
      expression = /\AUpdating .* done.\nAdding .*\n/m
      assert_match expression, logs
    end

    test "drop capability" do
      logs = capture_stdout do
        Fluent::CapCtl.new(["--drop", "chown"]).call
      end
      expression = /\AUpdating .* done.\nDropping .*\n/m
      assert_match expression, logs
    end

    test "get capability" do
      logs = capture_stdout do
        Fluent::CapCtl.new(["--get"]).call
      end
      expression = /\ACapabilities in .*,\nEffective:   .*\nInheritable: .*\nPermitted:   .*/m
      assert_match expression, logs
    end
  end

  sub_test_case "success with file" do
    test "clear capability" do
      logs = capture_stdout do
        Tempfile.create("fluent-cap-") do |tempfile|
          Fluent::CapCtl.new(["--clear-cap", "-f", tempfile.path]).call
        end
      end
      expression = /\AClear capabilities .*\n/m
      assert_match expression, logs
    end

    test "add capability" do
      logs = capture_stdout do
        Tempfile.create("fluent-cap-") do |tempfile|
          Fluent::CapCtl.new(["--add", "dac_override", "-f", tempfile.path]).call
        end
      end
      expression = /\AUpdating .* done.\nAdding .*\n/m
      assert_match expression, logs
    end

    test "drop capability" do
      logs = capture_stdout do
        Tempfile.create("fluent-cap-") do |tempfile|
          Fluent::CapCtl.new(["--drop", "chown", "-f", tempfile.path]).call
        end
      end
      expression = /\AUpdating .* done.\nDropping .*\n/m
      assert_match expression, logs
    end

    test "get capability" do
      logs = capture_stdout do
        Tempfile.create("fluent-cap-") do |tempfile|
          Fluent::CapCtl.new(["--get", "-f", tempfile.path]).call
        end
      end
      expression = /\ACapabilities in .*,\nEffective:   .*\nInheritable: .*\nPermitted:   .*/m
      assert_match expression, logs
    end
  end

  sub_test_case "invalid" do
    test "add capability" do
      assert_raise(ArgumentError) do
        Fluent::CapCtl.new(["--add", "nonexitent"]).call
      end
    end

    test "drop capability" do
      assert_raise(ArgumentError) do
        Fluent::CapCtl.new(["--drop", "invalid"]).call
      end
    end
  end
end