then:
        ideaProject.javaLanguageSettings.targetBytecodeVersion == JavaVersion.VERSION_1_5
        ideaProject.modules.find { it.name == 'root' }.javaLanguageSettings.targetBytecodeVersion == null
        ideaProject.modules.find { it.name == 'child1' }.javaLanguageSettings.targetBytecodeVersion == null
        ideaProject.modules.find { it.name == 'child2' }.javaLanguageSettings.targetBytecodeVersion == null

    private JavaVersion languageLevel;
    private JavaVersion targetBytecodeVersion;
    private DefaultInstalledJdk jdk;

    public DefaultIdeaJavaLanguageSettings setSourceLanguageLevel(JavaVersion languageLevel) {
        this.languageLevel = languageLevel;
        return this;
    }

    public DefaultIdeaJavaLanguageSettings setTargetBytecodeVersion(JavaVersion targetBytecodeVersion) {
        this.targetBytecodeVersion = targetBytecodeVersion;

        then:
        subprojectA.javaSourceSettings.targetBytecodeVersion == JavaVersion.VERSION_1_1
        subprojectB.javaSourceSettings.targetBytecodeVersion == JavaVersion.VERSION_1_2
        subprojectC.javaSourceSettings.targetBytecodeVersion == JavaVersion.VERSION_1_3
    }

import java.io.Serializable;

public class DefaultEclipseJavaSourceSettings implements Serializable {
    private JavaVersion sourceLanguageLevel;
    private JavaVersion targetBytecodeVersion;
    private DefaultInstalledJdk jdk;

    public DefaultEclipseJavaSourceSettings setSourceLanguageLevel(JavaVersion sourceLanguageLevel) {
        this.sourceLanguageLevel = sourceLanguageLevel;
        return this;

        project.getPlugins().apply(IdeaPlugin)
        def iml = Mock(IdeaModuleIml)
        def module = TestUtil.newInstance(IdeaModule, moduleProject, iml)
        expect:
        module.targetBytecodeVersion == null
    }

   def "target bytecode version is null if matching calculated idea project bytecode version"() {
       given:
       project.getPlugins().apply(IdeaPlugin)

        childProject.targetCompatibility = JavaVersion.VERSION_1_6
        anotherChildProject.targetCompatibility = JavaVersion.VERSION_1_7

        then:
        project.idea.project.targetBytecodeVersion == JavaVersion.VERSION_1_7
    }

    /**
     * to be in sync with current language level settings were we also use 1.6 as default.
     * */

                javaSourceSettings?.jdk?.javaHome
                withJava(javaSourceSettings?.jdk?.javaVersion)
                withJava(javaSourceSettings?.sourceLanguageLevel)
                withJava(javaSourceSettings?.targetBytecodeVersion)
                projectNatures.each {
                    it.id
                }
                projectDependencies.each {
                    it.exported
                    it.path
                }

        when:
        def ideaProject = loadIdeaProjectModel()

        then:
        ideaProject.javaLanguageSettings.languageLevel == JavaVersion.VERSION_1_8
        ideaProject.javaLanguageSettings.targetBytecodeVersion == JavaVersion.VERSION_1_8
    }

    private IdeaProject loadIdeaProjectModel() {
        withConnection { connection -> connection.getModel(IdeaProject) }
    }

                <td><literal>JavaVersion.JAVA_1_6</literal></td>
                <td><literal>project.sourceCompatibility</literal></td>
            </tr>
            <tr>
                <td>targetBytecodeVersion</td>
                <td><literal>JavaVersion.JAVA_1_6</literal></td>

     * the convention computation that is not compatible with Isolated Projects.
     */
    @Nullable
    public JavaVersion getRawTargetBytecodeVersion() {
        return targetBytecodeVersion;
    }