### Question:
DataTypeConstraintExpression implements DataTypeConstraintComponent { @Override public void setConstraintValueType(final String constraintValueType) { view.setPlaceholder(placeholderHelper.getPlaceholderSentence(constraintValueType)); } @Inject  DataTypeConstraintExpression(final View view,
                                        final ConstraintPlaceholderHelper placeholderHelper); @Override String getValue(); @Override void setValue(final String value); @Override void setConstraintValueType(final String constraintValueType); @Override Element getElement();  }### Answer:
@Test public void testSetConstraintValueType() { final String type = "string"; final String placeholder = "placeholder"; when(placeholderHelper.getPlaceholderSentence(type)).thenReturn(placeholder); constraintExpression.setConstraintValueType(type); verify(view).setPlaceholder(placeholder); }