### Question:
SpringValueExtractor { public boolean isSpringValue(String string) { if (StringUtils.isEmpty(string)) { return false; } return (string.startsWith("${") && string.endsWith("}")); }  SpringValue extract(String string); boolean isSpringValue(String string);  }### Answer:
@Test public void is_spring_value_returns_expected_values() { assertTrue(extractorToTest.isSpringValue("${a.bc.d}")); assertFalse(extractorToTest.isSpringValue(null)); assertFalse(extractorToTest.isSpringValue("")); assertFalse(extractorToTest.isSpringValue("{a.bc.d}")); assertFalse(extractorToTest.isSpringValue("${a.bc.d")); assertFalse(extractorToTest.isSpringValue("$a.bc.d}")); assertFalse(extractorToTest.isSpringValue("a.bc.d")); }