00A0; NO-BREAK SPACE
   1680; OGHAM SPACE MARK
   2000; EN QUAD
   2001; EM QUAD
   2002; EN SPACE
   2003; EM SPACE
   2004; THREE-PER-EM SPACE
   2005; FOUR-PER-EM SPACE
   2006; SIX-PER-EM SPACE
   2007; FIGURE SPACE
   2008; PUNCTUATION SPACE
   2009; THIN SPACE
   200A; HAIR SPACE
   200B; ZERO WIDTH SPACE
   202F; NARROW NO-BREAK SPACE
   205F; MEDIUM MATHEMATICAL SPACE

   0340; COMBINING GRAVE TONE MARK
   0341; COMBINING ACUTE TONE MARK
   200E; LEFT-TO-RIGHT MARK
   200F; RIGHT-TO-LEFT MARK
   202A; LEFT-TO-RIGHT EMBEDDING
   202B; RIGHT-TO-LEFT EMBEDDING
   202C; POP DIRECTIONAL FORMATTING
   202D; LEFT-TO-RIGHT OVERRIDE
   202E; RIGHT-TO-LEFT OVERRIDE
   206A; INHIBIT SYMMETRIC SWAPPING
   206B; ACTIVATE SYMMETRIC SWAPPING
   206C; INHIBIT ARABIC FORM SHAPING
   206D; ACTIVATE ARABIC FORM SHAPING

    assertThat(stringPrep("\u2ffb")).isNull()
  }

  @Test fun prohibitionChangeDisplayPropertiesOrDeprecated() {
    assertThat(stringPrep("\u0340")).isNull() // COMBINING GRAVE TONE MARK
    assertThat(stringPrep("\u200e")).isNull() // LEFT-TO-RIGHT MARK
    assertThat(stringPrep("\u206e")).isNull() // NATIONAL DIGIT SHAPES
    assertThat(stringPrep("\u206f")).isNull() // NOMINAL DIGIT SHAPES
  }

   0080-009F; [CONTROL CHARACTERS]
   06DD; ARABIC END OF AYAH
   070F; SYRIAC ABBREVIATION MARK
   180E; MONGOLIAN VOWEL SEPARATOR
   200C; ZERO WIDTH NON-JOINER
   200D; ZERO WIDTH JOINER
   2028; LINE SEPARATOR
   2029; PARAGRAPH SEPARATOR
   2060; WORD JOINER
   2061; FUNCTION APPLICATION
   2062; INVISIBLE TIMES
   2063; INVISIBLE SEPARATOR
   206A-206F; [CONTROL CHARACTERS]
   FEFF; ZERO WIDTH NO-BREAK SPACE