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

        ideaProject.javaLanguageSettings.targetBytecodeVersion == JavaVersion.VERSION_1_5
        ideaProject.modules.find { it.name == 'test-project' }.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
    }

        IdeaLanguageLevel languageLevel = resolveRootLanguageLevel(ideaProjectExt, allIsolatedIdeaModules);
        JavaVersion targetBytecodeVersion = resolveRootTargetBytecodeVersion(ideaProjectExt, allIsolatedIdeaModules);

        DefaultIdeaProject out = buildWithoutChildren(ideaProjectExt, languageLevel, targetBytecodeVersion);

        // Important to build GradleProject after the IsolatedIdeaModuleInternal requests,

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;

        "target" | "targetCompatibility" | "targetBytecodeVersion" | "java"      | JavaBasePlugin
        "source" | "sourceCompatibility" | "sourceLanguageLevel"   | "scala"     | ScalaBasePlugin
        "target" | "targetCompatibility" | "targetBytecodeVersion" | "scala"     | ScalaBasePlugin

        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.
     * */

        originalIdeaModel.javaLanguageSettings.targetBytecodeVersion == JavaVersion.VERSION_1_8
        originalIdeaModel.modules.name == ["root", "lib1", "lib2"]
        originalIdeaModel.modules[1].javaLanguageSettings.languageLevel == JavaVersion.VERSION_1_7
        originalIdeaModel.modules[1].javaLanguageSettings.targetBytecodeVersion == JavaVersion.VERSION_1_7