rake 测试准备：NoMethodError：nil:NilClass 的未定义方法“[]”

Question

当我运行 rake db:test:prepare 时，我总是收到以下错误。什么会导致这种情况？rake db:create 工作正常。

 Adam-MacBook-Pro:katy adam$ bundle exec rake db:test:prepare
    rake aborted!
    NoMethodError: undefined method `[]' for nil:NilClass
    /Users/adam/.rvm/gems/ruby-2.2.2/gems/activerecord-4.2.4/lib/active_record/tasks/database_tasks.rb:163:in `purge'
    /Users/adam/.rvm/gems/ruby-2.2.2/gems/activerecord-4.2.4/lib/active_record/railties/databases.rake:356:in `block (3 levels) in <top (required)>'
    /Users/adam/.rvm/gems/ruby-2.2.2/gems/activerecord-4.2.4/lib/active_record/railties/databases.rake:362:in `block (3 levels) in <top (required)>'
    /Users/adam/.rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `eval'
    /Users/adam/.rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `<main>'

数据库.yml

<%= Rails.env %>:
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV['DB_POOL'] || 5 %>
  username: <%= ENV['DB_USER'] || 'root' %>
  password: <%= ENV['DB_PASSWORD'] || nil %>
  timeout: <%= ENV['DB_TIMEOUT'] || 5000 %>
  host: <%= ENV['DB_HOST'] || 'localhost' %>
  port: <%= ENV['DB_PORT'] || 3306 %>
  database: <%= ENV['DB_NAME'] || "website#{Rails.env}" %>

Answer 1

RAILS_ENV尝试在运行 rake 命令时指定：

RAILS_ENV=test bundle exec rake db:test:prepare