@TaskAction def exec() {
                    output.text = duration.toString()
                }
            }

            task myTask(type: MyTask) {
                duration = Duration.ofMinutes(1)
                output = project.file("build/output.txt")
            }
        """

        when:
        run ':myTask'

        then:
        executedAndNotSkipped ':myTask'

        given:
        file('files/a/one.txt').createFile()
        file('files/b/two.txt').createFile()
        buildFile """
            def files = files('files/a', 'files/b').minus(files('files/b'))
            task copy(type: Copy) {
                from files
                into 'dest'
            }
        """

        when:
        run 'copy'

        then:

        given:
        file('files/one.txt').createFile()
        file('files/a/two.txt').createFile()
        file('files/b/ignore.txt').createFile()
        buildFile """
            def files = fileTree(dir: 'files').minus(fileTree(dir: 'files/b'))
            task copy(type: Copy) {
                from files
                into 'dest'
            }
        """

        when:
        run 'copy'

        then:

        TestFileCollection collection1 = new TestFileCollection(file1, file2)
        TestFileCollection collection2 = new TestFileCollection(file2, file3)

        when:
        FileCollection difference = collection1.minus(collection2)

        then:
        difference.files == toLinkedSet(file1)
    }

    def "can subtract a collections using - operator"() {
        File file1 = new File("f1")