public <T> void testWhere_wildcardSelfMapping() {
    TypeResolver resolver = new TypeResolver();
    Type t = aWildcardType();
    assertEquals(t, resolver.where(t, t).resolveType(t));
  }

  public <T> void testWhere_duplicateMapping() {
    Type t = aTypeVariable();
    TypeResolver resolver = new TypeResolver().where(t, String.class);
    assertThrows(IllegalArgumentException.class, () -> resolver.where(t, String.class));
  }