assertProblemFree(collector);

        assertEquals("/path/to/home", out.getProperties().get("outputDirectory"));
    }

    @Test
    public void envarExpressionThatEvaluatesToNullReturnsTheLiteralString() throws Exception {

        Map<String, String> modelProperties = new HashMap<>();
        modelProperties.put("outputDirectory", "${env.DOES_NOT_EXIST}");