Tag(String spec) {
        String[] labelParts = spec.trim().split("\\s*=\\s*");
        if (labelParts.length != 2) {
            throw new InvalidConfigurationException(String.format("Invalid tag specification: '%s'", spec));
        }
        this.key = labelParts[0];
        this.value = labelParts[1];
    }
@Test
    public void tag() {
        // given
        String tag = "key=value";

        // when
        Tag result = new Tag(tag);

        // then
        assertEquals("key", result.getKey());
        assertEquals("value", result.getValue());
    }