### Question:
PropertyImpl implements Property { public static Property parse(String keyValue, ConfigFormat configFormat, DeclaringComponent source) { boolean temp = isTempProperty(keyValue); int separatorIndex = findSeparatorIndexIn(keyValue); if (separatorIndex < 0) { throw new IllegalArgumentException("Incorrect delimiter in '" + keyValue + "' in '" + source + "'\nProperty must contain ':' or '=' as delimiter."); } String key = keyValue.substring(temp ? TEMP_VALUE.length() : 0, separatorIndex).trim(); String value = keyValue.substring(separatorIndex + 1).trim(); return new PropertyImpl(key, value, temp, configFormat, source); }  static Property parse(String keyValue, ConfigFormat configFormat, DeclaringComponent source); static Property property(String key, String value, ConfigFormat configFormat, DeclaringComponent source); static int findSeparatorIndexIn(String keyValue); static boolean isComment(String line); static boolean isTempProperty(String line); @Override Property resolveBy(Resolver resolver, DeclaringComponent root); @Override String toString();  }### Answer:
@Test void failOnMissingSeparator() { assertThrows(IllegalArgumentException.class, () -> parse("key value", PROPERTIES, yamlSource)); }