when:
        buildOptions.getJavaInstallationsFromEnvironment() >> []
        def directories = supplier.get()

        then:
        directories.isEmpty()
    }

    def "supplies single installations for single path"() {
        when:
        buildOptions.getJavaInstallationsFromEnvironment() >> ["JDK8"]
        def directories = supplier.get()

        then:

@ServiceScope({ Scope.Build.class, Scope.Global.class })
public interface ToolchainConfiguration {
    String AUTO_DETECT = "org.gradle.java.installations.auto-detect";

    Collection<String> getJavaInstallationsFromEnvironment();
    void setJavaInstallationsFromEnvironment(Collection<String> installations);

    Collection<String> getInstallationsFromPaths();
    void setInstallationsFromPaths(Collection<String> installations);

        this.javaInstallationsFromEnvironment = Collections.emptyList();
        this.installationsFromPaths = Collections.emptyList();
    }

    @Override
    public Collection<String> getJavaInstallationsFromEnvironment() {
        return javaInstallationsFromEnvironment;
    }

    @Override
    public void setJavaInstallationsFromEnvironment(Collection<String> javaInstallationsFromEnvironment) {

    }

    @Override
    public Set<InstallationLocation> get() {
        final Collection<String> possibleInstallations = buildOptions.getJavaInstallationsFromEnvironment();
        return possibleInstallations.stream().map(this::resolveEnvironmentVariable)
            .filter(Optional::isPresent)
            .map(Optional::get)
            .collect(Collectors.toSet());
    }

        this.providerFactory = providerFactory;
        this.systemProperties = systemProperties;
    }

    @Override
    public Collection<String> getJavaInstallationsFromEnvironment() {
        return Arrays.asList(providerFactory.gradleProperty(EnvironmentVariableListInstallationSupplier.JAVA_INSTALLATIONS_FROM_ENV_PROPERTY).getOrElse("").split(","));
    }

    @Override