Add isolated tests for Context#git_editor method

test/context_test.rb

+require 'helper'
+
+class ContextTest < Test::Unit::TestCase
+  class Context
+    include Hub::Context
+
+    def initialize(&block)
+      @git_reader = Hub::Context::GitReader.new('git', &block)
+    end
+
+    public :git_editor
+  end
+
+  attr_reader :context
+
+  def setup
+    super
+    @stubs = {}
+    @context = Context.new do |_, cmd|
+      @stubs.fetch(cmd)
+    end
+  end
+
+  def test_editor
+    stub_command_output 'var GIT_EDITOR', 'vim'
+    assert_equal %w'vim', context.git_editor
+  end
+
+  def test_editor_with_argument
+    stub_command_output 'var GIT_EDITOR', 'subl -w'
+    assert_equal %w'subl -w', context.git_editor
+  end
+
+  def test_editor_with_spaces
+    stub_command_output 'var GIT_EDITOR', '"my editor" -w arg2'
+    assert_equal %w'my\ editor -w arg2', context.git_editor
+  end
+
+  def test_editor_with_tilde
+    stub_command_output 'var GIT_EDITOR', '~/bin/vi'
+    with_env('HOME', '/home/mislav') do
+      assert_equal %w'/home/mislav/bin/vi', context.git_editor
+    end
+  end
+
+  def test_editor_with_env_variable
+    stub_command_output 'var GIT_EDITOR', '$EDITOR'
+    with_env('EDITOR', 'subl -w') do
+      assert_equal %w'subl -w', context.git_editor
+    end
+  end
+
+  private
+
+  def stub_command_output(cmd, value)
+    @stubs[cmd] = value.nil? ? nil : value.to_s
+  end
+
+  def with_env(name, value)
+    dir, ENV[name] = ENV[name], value
+    yield
+  ensure
+    ENV[name] = dir
+  end
+end