Grails 2.2.4单元测试标准，调用不同（Collection）

Question

我正在尝试对最终调用Criteria API的不同（Collection）方法的服务方法进行单元测试（即，它调用带有Collection的distinct（）版本）。我收到以下错误：

  

没有方法签名：greenfield224.BookService.distinct（）适用于参数类型：（java.util.ArrayList）值：[[id，author，title，publisher]]

如果我更改服务方法，使它使用接受单个String属性名称的distinct（）版本，我不会收到错误。但是，如果该单个属性名称为“id”，则它在单元测试中不返回任何内容。

我想知道这是否是Grails 2.2.4测试框架中的错误，或者我是否只是不了解某些内容。单元测试可能不支持使用distinct（）方法吗？ （顺便说一下，等效的集成测试工作正常）。以下是一些演示此问题的示例代码：

class Book {
    Long id
    String subject
    String author
    String publisher
    String title

    static constraints = {
        subject nullable: true
        author nullable: true
        publisher nullable: true
        title nullable: true
    }
}

class BookService {

    def findSimilarBooks(Book book) {
        def results = Book.withCriteria {
            eq('subject', book.subject)
            order('title')
            order('author')

            projections {
                //this line blows up in a unit test
                distinct(['id', 'author', 'title', 'publisher'])
            }
        }

        return results.collect {
            [id:it[0], author:it[1], title:it[2], publisher:it[3]]
        }
    }
}

@TestFor(BookService)
@Mock(Book)
class BookServiceSpec extends Specification {

    def "findSimilarBooks works properly"() {
        setup:
        def math = new Book(id:1, title:"Mathematics for Nonmathematicians", subject: "Math", author:"Morris Kline", publisher:"Somehouse")
        def philosophy = new Book(id:2, title:"The Problems of Philosophy", subject: "Philosophy", author:"Bertrand Russell", publisher:"Ye Olde House of Mutton")
        def investing = new Book(id:3, title:"The Intelligent Investor", subject: "investing", author:"Ben Graham", publisher:"Investors Anonymous")
        def qed = new Book(id:4, title:"Q.E.D.", subject: "Math", author:"Burkard Polster", publisher: "Wooden Books")
        def books = [math, philosophy, investing, qed]
        books*.save(failOnError: true)

        when:
        def results = service.findSimilarBooks(math)

        then:
        results.size() == 2
    }
}