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Testing Custom RSpec Authorization Matchers in CanCan

This test suite validates the custom RSpec matcher ‘be_able_to’ in the CanCan authorization library. It ensures proper delegation of permission checks and verifies accurate error message generation for authorization failures. The tests confirm the integration between CanCan’s permission system and RSpec’s expectation syntax.

Test Coverage Overview

The test suite provides comprehensive coverage of the ‘be_able_to’ matcher functionality:

Verification of proper delegation to the can? method
Testing of failure message formatting for positive assertions
Validation of failure message formatting for negative assertions
Handling of multiple arguments in permission checks

Implementation Analysis

The testing approach utilizes RSpec’s behavior-driven development patterns with mock objects and expectation syntax. The implementation leverages RSpec’s built-in matcher framework to extend CanCan’s authorization checks with natural language assertions. Mock objects are used to isolate the matcher behavior from actual authorization logic.

Technical Details

Testing Framework: RSpec
Mocking Library: Built-in RSpec mocks
Test Pattern: Unit tests with isolation
Dependencies: spec_helper for test configuration
Custom Matcher: be_able_to for authorization assertions

Best Practices Demonstrated

The test suite exemplifies several testing best practices in Ruby and RSpec:

Isolated test cases with clear, single responsibility
Proper use of mocking to test behavior independently
Descriptive test names that document functionality
Comprehensive error message testing
Consistent test structure and organization

ryanb/cancan

spec/cancan/matchers_spec.rb

            
require "spec_helper"

describe "be_able_to" do
  it "delegates to can?" do
    object = Object.new
    mock(object).can?(:read, 123) { true }
    object.should be_able_to(:read, 123)
  end

  it "reports a nice failure message for should" do
    object = Object.new
    mock(object).can?(:read, 123) { false }
    expect do
      object.should be_able_to(:read, 123)
    end.should raise_error('expected to be able to :read 123')
  end

  it "reports a nice failure message for should not" do
    object = Object.new
    mock(object).can?(:read, 123) { true }
    expect do
      object.should_not be_able_to(:read, 123)
    end.should raise_error('expected not to be able to :read 123')
  end

  it "delegates additional arguments to can? and reports in failure message" do
    object = Object.new
    mock(object).can?(:read, 123, 456) { false }
    expect do
      object.should be_able_to(:read, 123, 456)
    end.should raise_error('expected to be able to :read 123 456')
  end
end