### Question:
TemplatedEmailMessageBuilder { public TemplatedEmailMessageBuilder withSubject(final String subject) { Assert.notNull(subject, "Null was passed as an argument for parameter 'subject'."); this.subject = subject; return this; } TemplatedEmailMessageBuilder(final String from,
                                        final String to,
                                        final String templateId,
                                        final Map<String, ?> variables,
                                        final Set<SpiEmailNotificationFileAttachment> fileAttachments); TemplatedEmailMessageBuilder withLocale(final Locale locale); TemplatedEmailMessageBuilder withSubject(final String subject); TemplatedEmailMessage build();  }### Answer:
@Test public void withSubjectWithIllegalArgument() { assertThatThrownBy(() -> new TemplatedEmailMessageBuilder( uuid(), uuid(), uuid(), Collections.emptyMap(), Collections.emptySet() ).withSubject(null) ).isInstanceOf(IllegalArgumentException.class); }