### Question:
StripeTextUtils { public static boolean isBlank(@Nullable String value) { return value == null || value.trim().length() == 0; }  @Nullable static String nullIfBlank(@Nullable String value); static boolean isBlank(@Nullable String value); @Nullable static String removeSpacesAndHyphens(@Nullable String cardNumberWithSpaces);  }### Answer:
@Test public void isBlankShouldPassIfNull() { assertTrue(StripeTextUtils.isBlank(null)); }
@Test public void isBlankShouldPassIfEmpty() { assertTrue(StripeTextUtils.isBlank("")); }
@Test public void isBlankShouldPassIfSpace() { assertTrue(StripeTextUtils.isBlank(" ")); }
@Test public void isBlankShouldPassIfSpaces() { assertTrue(StripeTextUtils.isBlank(" ")); }
@Test public void isBlankShouldPassIfTab() { assertTrue(StripeTextUtils.isBlank(" ")); }
@Test public void isBlankShouldFailIfNumber() { assertFalse(StripeTextUtils.isBlank("0")); }
@Test public void isBlankShouldFailIfLetters() { assertFalse(StripeTextUtils.isBlank("abc")); }